Friday, October 11, 2013


Sample test paper EA Engineering Assistants in AIR and DD 2010
Containing physics MCQ Questions on
electrical field
magnetic wires
magnetic field intensity
electrical coil
electrical charges
magnetic induction
induction magnetic
electrical magnetic
magnetic plates
1. Which one of the following physical quantities, is not defined in the terms of force per unit area:
(a) pressure
(b) strain
(c) stress
(d) Young’s modulus
2. The distance moved by a moving body is equal to:
(a) area between the distance-time graph and distance axis
(b) area between the speed-time graph and time axis
(c) area between the distance-time graph and time axis
(d) area between the speed-time graph and distance axis.
3. A beaker containing water weighs 100 gm. It is placed on the pan of a balance and a piece of metal weighing 70 gm. and having a volume of 10cc. is placed inside the water in the beaker. The weight of the beaker and the metal would be :
(a) 170gm.
(c) 100gm.
4. For the same kinetic energy, the momentum shall be maximum for:
(a) electron
(b) proton
(c) deuteron
(d) alpha particle
5. The common balance works on the principle of equality of:
(a) forces
(b) moments of forces
(c) masses
(d) masses of pans
6. A particle moves in a circle of radius R with a constant speed under a centripetal force F. The work done in completing a full circle is:
(a) 2RF
(b) ΠR2F
(c) 2ΠRF
7. When two quantities are plotted on the graph paper against each other and the result so obtained is a st. line, then
(a) Both the quantities are equal
(b) The quantities are inversely proportional to each other
(c) Sum of both is zero
(d) The quantities are proportional to each other
8. What is the order of magnitude of 260°?
(b) 104
(d) 10
9. The maximum value of g is:
(a) At the poles
(b) At the top of the Mount Everest
(c) At the equator
(d) Below the sea level
10. A fixed volume of gas at 27°C exerts a pressure of 750 mm. If the gas is heated to a pressure of 1500mm., temperature must be:
(a) 600°C
(b) 327°C
(c) 54°C
(d) 13.5°C
11. A body of mass 2 kg acted upon by a constant force, travels a distance of 3 metres in the first second and a further distance of meter in the next second. The force acting on the body is?
(a) 12 Newtons
(b) 8 Newtons
(c) 4 Newtons
(d) 1 Newton
12. Two forces each equal to P acting at a point have no resultant. The angle between the two forces must be equal to:
(b) 90°
(d) 120°
13. A jet engine works on the principle of:
(a) conservation of energy
(b) conservation of momentum
(c) conservation of mass
(d) conservation of temperature
14. A sharp knife cuts much better than a blunt one because?
(a) Area of sharp knife is much less than the area of the blunt one
(b) sharp knife is brighter
(c) sharp knife is colder
(d) sharp knife is costly
15. A man carries a heavy box on his head on a horizontal plane from one place to another.
In this he does?
(a) maximum work
(b) no work
(c) negative work
(d) minimum work
16. The bob of a second’s pendulum is replaced by another bob of double mass. The new time period will be:
(a) 4 sec.
(c) 2 sec.
(b) 1 sec
(d) 3 sec.
17.A device for measuring temperatures at a distance is
(a) gas thermometer
(b) mercury thermometer
(c) radiation
(d) maximum-minimum thermometer
18. A piece of ice is floating in a concentrated solution of common salt (in water) in a pot. When ice melts completely, the level of solution will:
(a) go up
(b) remain the same
(c) go down
(d) first go up then go down
19. A radioactive source has a half-life of 30 days. During a period of 90 days the fraction of atoms that have decayed would be
(b) 87.5%
(d) 50%
20. A black body emits:
(a) radiations of all wavelengths
(b) no radiations
(c) radiations of only one wavelength
(d) radiations of selected wavelengths
21. A near sighted person cannot see distinctly beyond 50 cm. from his eye. The power in diopter of spectacle lenses which will enable him to see distant objects clearly is
(a) +50
(b) —50
(c) +2
(d) —2
22. Size of a nucleus is of the order of?
(b) 10-14m
(d) 10-6m
23. The freezing point on a thermometer is marked as 20° and the boiling point as 150°C. A temperature of 60°C on this thermometer will be read as:
(b) 65°
(d) 110°
24. In isothermal expansion of an ideal gas:
(a) heat content remains constant
(b) temperature remains constant
(c) both heat content and temperature remain constant
(d) pressure and temperature of the gas remain constant
25. A man standing between two cliffs hears the first echo of a sound after 2 sec. and the second echo 3 sec. after the initial sound. If the speed of sound be 330 m/sec. the distance between the two cliffs should be
(a)1650 m.
(b)990 m.
(c)825 m
(d) 660 m.
26. In a resonance tube experiment the first resonance is obtained for 10 cm. of air column and the second for 32 cm. The end correction for this apparatus is equal to?
(a)0.5 cm
(b)1.0 cm
(c)1.5 cm
(d) 2 cm
27. The ratio of the specific heat of air at constant pressure to its specific heat at constant volume is?
(a) zero
(b) greater than one
(c) less than one
(d) equal to one
28. A convex lens has a focal length of 10 cm. When it is immersed in water it will behave
(a) a convex tens of 10 cm. focal length
(b) a concave lens of 10 cm. focal length
(c) a convex lens of focal length greater than 10cm.
(d) a convex lens of focal length less than 10 cm.
29. Two particles having charges q1 and q2 when kept at a certain distance exert a force F on each other. If the distance between the two particles is reduced to half and the charge on each particle is doubled the force between the particles would be ?
30. A small magnet is placed perpendicular to a constant magnetic field. The forces acting on the magnet will result in?
(a) rotation
(b) translation
(c) no motion at all
(d) rotation as well as translation
31. A hollow metallic sphere is charged. Inside the sphere?
(a) the potential is zero but the electric field is finite
(b) the electric field is zero but the potential is finite
(c) both the electric field and the potential are finite
(d) both the electric field and the potential are zero
32. Two electric lamps each of 100 watts 220 V are connected in series to a supply of 220 volts. The power consumed would be:
(a)100 Watts
(b) 200 Watts
(c)25 Watts
(d) 50 Watts
33. A transformer is:
(a) a device for stepping up D.C.
(b) a generator of current
(c) device for converting direct current into alternating current
(d) a device for stepping up or down the voltage of A.C. supply
34. Transistor act as a?
(a) conductor
(b) semi-conductor
(c) insulator
(d) thermionic valve
35. The sky is blue because:
(a) there is more blue light in the sunlight
(b) of scattering of sunlight by air molecules in the atmosphere
(c) of scattering of sunlight by dust particles in the atmosphere
(d) other colours are absorbed by heavenly bodies
36. A cyclonic storm is indicated by a change in the atmospheric pressure. In atmospheric
pressure there is a:
(a)sudden rise
(b) gradual rise
(c)sudden fall
(d) gradual fall
37. The electric field inside a hollow conducting sphere will ?
(a) increases towards the centre
(b) decreases towards the centre
(c) is finite and constant throughout
(d) is zero
38. Imperfect gases are those:
(a) which contain impurities
(b) which do not obey Charle’s and Boyle’s laws
(c) whose molecules are not spherical
(d) whose molecules cannot be regarded as point masses
39. Sonar is a device for:
(a) location and ranging of aircraft’s
(b) location and ranging submarines
(c) producing a musical note of high quality
(d) measuring frequency of musical notes
40. Cyclotron is a device to produce:
(a) atomic energy
(b) high energy electrons
(c) high energy photons
(d) high energy protons
41. Which one of the following is not a vector?
(a) Velocity
(b) Acceleration
(c) Force
(d) Energy
42. Two steel balls of mass 1 kg. and 2kg. and a lead ball of 10kg. are released together from the top of tower 30 metres high. Assuming the path to be in vacuum
(a) the lead ball reaches the ground earlier
(b) the 1 kg. steel bail reaches the ground earlier
(c) all the balls reach the ground simultaneously
(d) the 2 kg. steel ball reaches the ground earlier
43. After a watch has been wound, it?
(a) has great energy stored in it
(b) possesses mechanical potential energy stored in it
(c) has eletrical energy stored in it
(d) has no energy in it
44. Two plane mirrors are set at right angles and a flower is placed in any position in between the mirrors. The number of images of the flower which will be seen is?
(b) two
(d) four
(a) one
(c) three
45. In which of the following cases total internal reflection cannot be obtained?
(a) ray going from water to glass
(b) a ray going from glass to water
(c) a ray going from glass to air
(d) a ray going from water to air.
46. When white light passes through a glass prism, we get a spectrum on the other side of the prism. In the emergent beam the ray which is deviated least is
(a) the violet ray
(b) the red ray
(c) the green ray
(d) the yellow ray
47. Magnetic storms are due to
(a) the rotation of the earth
(b) the revolution of the earth
(c) the rainy season
(d) the appearance off Sun spots
48. For dynamo which one of the following statements is correct ?
(a) It converts the electrical energy into light energy
(b) It converts the kinetic energy into heat energy
(c) It converts the mechanical energy into electrical energy
(d) Jt converts the electrical energy into mechanical energy.
49. In a transformer the immediate cause of the induced A. C. in the secondary coil is?
(a) a varying electric field
(b) a varying magnetic field
(e) a motion of the secondary coil
(d) efficiency of the operator
50.A dynamo actually acts as a?
(a) converter of energy
(b) source of electric charge
(c) source of magnetic charge
(d) source of energy
Quiz MCQ Objective Question About Current Magnetic Field For  Engineering Assistants in All India Radio ( Akashvani AIR) and Doordarshan (DD)
1. A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its
plane becomes    ?
(a) inclined at 45° to the magnetic field
(b) inclined at any arbitrary angle to the
magnetic field
(c)   parallel to the magnetic field
(d)   perpendicular to magnetic field
2. Tesla is the unit of
(a)    magnetic flux
(b)    magnetic field
(c)    magnetic induction
(d)    magnetic moment
3. Energy in a current carrying coil is stored in the
form of   ?
(a) electric field
(b) magnetic field
(c) dielectric strength
(d) heat
4. The total charge induced in a conducting loop when it is moved in magnetic field depends on?
(a) the rate of change of magnetic flux
(b) initial magnetic flux only
(c) the total change in magnetic flux
(d) final magnetic flux only.
5. The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is 10-3 T. The field of induction at a distance 12 cm from the current will be ?
(a) 3.33 x 10-4 T
(b) 1.11x 10-4 T
(c) 3×10-3 T
(d) 9×10-3 T
6. A charge moving with velocity v in X-direction is subjected to a field of magnetic induction in negative X-direction. As a result, the charge will
(a) remain unaffected
(b) start moving in a circular path in Y—Z plane
(c) retard along X-axis
(d) moving along a helical path around X-axis
7. A uniform magnetic field acts right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2cm. If the speed of electrons is doubled, then the radius of the circular path will be ?
(a)2.0 cm
(b) 0.5 cm
(d) 1.0cm
8. A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to magnetic field B. The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre in the same plane with
the same B is
(a)25 keV
(b) 50 keV
(c)200 keV
(d) 100 keV
9. A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in uniform magnetic field of induction 2 Tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is ?
(a) 2.4N
(b) 1.2N
(c) 3.0 N
(d) 2.0 N
10. To convert a galvanometer into an ammeter, one needs to connect a ?
(a) low resistance in parallel
(b) high resistance in parallel
(c) low resistance in series
(d) high resistance in series.
11. A coil carrying electric current is placed in uniform magnetic field
(a) torque is formed
(B) e.m.f is induced
(c) both (a) and (b) are correct
(d) none of the above
12. The magnetic field at a distance ‘r’ from a long wire carrying current ‘i’ is 0.4 Tesla. The magnetic field at a distance ‘2r’ is ?
(b) 0.8 Tesla
(c)0.1 Tesla
(d) 1.6 Tesla
13. A electron enters a region where magnetic (B) and electric (E) fields are mutually
perpendicular, then ?
(a) it will always move in the direction of B
(b) it will always move in the direction of E
(c) it always possesses circular motion
(d) it can go un deflected also.
14. A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of I mm diameter carrying same current. The strength of magnetic field far away is?
(a) twice the earlier value
(b) same as the earlier value
(c) one-half of the earlier value
(d) one-quarter of the earlier value
15. At what distance from a long straight wire carrying a current of 12 A will the magnetic field
be equal to 3×10-6 Wb/metre Square
(a) 8×10-2 m
(b) 12×10-2 m
(c)18x 10-2 m
(d) 24×10-2 m
16. An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to ?
(a) √(B/v)
(b) B/v
(c) √(v/B)
17. A 10 eV electron is circulating in a plane at right angles to a uniform field at magnetic induction 10-4 Wb/m2 (= 1.0 gauss). The orbital radius of the electron is ?
(a) 12cm
(b) 16cm
(c) 11cm
(d) 18cm
18. A galvanometer acting as a voltmeter will have?
(a) a low resistance in series with its coil.
(b) a high resistance in parallel with its coil
(c) a high resistance in series with its coil
(d) a low resistance in parallel with its coil
19. A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength 20 Vm-1 and 0.5 T respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be?
(a) 8m/s
(b) 20 m/s
(c) 40m/s
(d) 1/40 m/s
20. A galvanometer of resistance 20 Ohms gives full scale deflection with a current of 0.004 A. To convert it into an ammeter of range 1 A, the required shunt resistance should be?
(a) 0.38 Ohms
(b) 0.21 Ohms
(c) 0.08 Ohms
(d) 0.05 Ohms
21. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is ?
(a) 4B
(b) B/2
(c) B
(d) 2B
22. A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particle will
(a) continue to move due east
(b) move in a circular orbit with its speed unchanged
(c) move in a circular orbit with its speed increased
(d) gets deflected vertically upwards.
23. Two long parallel wires are at a distance of 1 metre. Both of them carry one ampere of current The force of attraction per unit length between the two wires is?
(a)2 x10-7 N/m
(b) 2 x10-8 N/m
(c) 5×10-8 N/m
(d)10-7 N/m
24. A galvanometer having a resistance of 8 ohms is shunted by a wire of resistance 2 ohms. If the total current is 1 amp, the part of it passing through the shunt will be?
(a)0.25 amp
(b) 0.8 amp
(c)0.2 amp
(d) 0.5 amp
25. A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be?
26. Magnetic field intensity in the centre of coil of 50 turns, radius 0.5 m and carrying a current of
2A is ?
(a) 0.5 x 10-5 T
(b) 1.25x 10-4 T
(c) 3x 10-5 T
(c) 4 x 10-5 T
27. When a proton is accelerated through I V, then its kinetic energy will be?
(a)1840 eV
(b) 13.6eV
(c)1 eV
(d) 0.54eV
28. If a long hollow copper pipe carries a current,thin magnetic field is produced
(a)inside the pipe only
(b)outside the pipe only
(c)both inside and outside the pipe
(d) no where
29. A charged particle moves through a magnetic field in a direction perpendicular to it. Then the
(a) velocity remains unchanged
(b) speed of the particle remains unchanged
(c) direction of the particle remains unchanged
(d) acceleration remains unchanged
30. Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance of 5 m between them. If P and Q carry current of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half-way between the wires is ?
31. A proton moving with a velocity 3 x 105 m/s enters a magnetic field of 0.3 Tesla at an angle of 30° with the field. The radius of curvature of its path will be (e/m for proton – 108 C/kg)
(b) 0.5 cm
(c)0.02 cm
(d) 1.25 cm
32. A charged particle of charge q and mass m enters perpendicularly in a magnetic field B. Kinetic energy of the particle is E; then frequency of rotation is?
(b) qB/2m∏
(d) qB/2E∏
33. A galvanometer can be converted into a voltmeter by connecting?
(a) A high resistance in parallel
(b) A low resistance in series
(c) A high resistance in series
(d) A low resistance in parallel
34. A wire carries a current. Maintaining the same current it is bent first to form a circular plane coil of one turn which produces a magnetic field B at the centre of the coil. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre of the double loop, caused by the same current is ?
(b) B /4
(c) B/2
(d) 2B
35.A bar magnet is oscillating in earth’s magnetic field with a period T. What happens to its period of motion, if its mass is quadruped ?
(a) Motion remains simple harmonic with new period =T/2
(b) Motion remains simple harmonic with new period = 2 T
(c) Motion remains simple harmonic with new period =4T
(d) Motion remains simple harmonic and the period stays nearly constant
36. The work done in turning a magnet of magnetic moment M by an angle of 90° from the meridian, is n times the corresponding work done to turn it through an angle of 60°.
The value of n is given by
(b) 1
(c) 0.5
(d) 0.25
37 . For protecting a sensitive equipment from the external electric arc, it should be ?
(a) Wrapped with insulation around it when passing current through it
(b) Placed inside an iron can
(c) Surrounded with fine copper sheet
(d) Placed inside an aluminium can
38. If a diamagnetic substance is brought near north or south pole of a bar magnet, it is?
(a) attracted by the poles
(b) repelled by the poles
(c) repelled by north pole and attracted by the south pole
(d) attracted by the north pole and repelled by the south pole
39. Current i is flowing in a coil of area A and number of turns N, then magnetic moment of
the coil is M= ?
(a) NiA
(b) Ni/A
(d) N2Ai
40. Two magnets of magnetic moments M and 2M are placed in a vibration magnetometer, with the identical poles in the same direction. The time period of vibration is T1. If the magnets are placed with opposite poles together and vibrate with time period T2 then ?
(a) T2 is infinite
(b) T2=T1
(d) T2 is less than T1
41. A diamagnetic material in a magnetic field moves
(a) perpendicular to the field
(b) from stronger to the weaker pans of the field
(c) from weaker to the stronger parts of the field
(d) in none of the above directions
42. According to Curie’s law, the magnetic susceptibility of a substance at an absolute
temperature T is proportional to?
(a) T2
(b) 1/T
(c) T
(d) 1/T2
Free Online Quiz Objective MCQ Questions on Solids and Semiconductor devices Like Diodes transistors Amplifiers
Basic Electronics Quiz
Semiconductor Quiz
1.A p-n junction is said to be forward biased, when
(a)    the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor
(b)    the positive pole of the battery is joined to the n-semiconductor and negative  pole of the battery is joined to the p-semiconductor
(c)    the positive pole of the battery is connected to n- semiconductor and p- semiconductor
(d)    a mechanical force is applied in the forward direction
Ans :a
2. At    absolute zero, Si acts as ?
(a)  non-metal
(b) metal
(c) insulator
(d) none of these
Ans :a
3. When N-type semiconductor is heated ?
(a) number of electrons increases while that of holes decreases
(b) number of holes increases while that of electrons decreases
(c) number of electrons and holes remain same
(d) number of electron and holes increases equally.
Ans :d
4. Radiowaves of constant amplitude can be generated with
(a) FET
(b) filter
(c) rectifier
(d) oscillator
Ans :d
5. In a common base amplifier the phase difference between the input signal voltage and the output
voltage is ?
(a) 0
(b) pi/4
(d) p
Ans :d
6. When a triode is used as an amplifier the phase difference between the input signal voltage and
the output is   ?
(a) 0
(c) pi/2
Ans :b
7. The depletion layer in the P-N junction region is
caused by?
(a) drift of holes
(b) diffusion of charge carriers
(c) migration of impurity ions
(d) drift of electrons
Ans: b
8. The following truth table corresponds to which Logic gate
(b) OR
(d) XOR
Ans :b
9. To use a transistor as an amplifier
(a) The emitter base junction is forward biased and the base collector junction is reversed biased
(b) no bias voltage is required
(c) both junction are forward biased
(d) both junctions are reversed biased.
Ans :a
10. Which one of the following is the weakest kind of the bonding in solids
(a) ionic
(b) metallic
(c) Vander Walls
(d) covalent
Ans :c
11.For amplification by a triode, the signal to be amplified is given to
(a) the cathode
(b) the grid
(c) the glass-envelope
(d) the anode
Ans :b
12. A piece of copper and other of germanium are cooled from the room temperature to 80K, then
(a) resistance of each will increase
(b) resistance of copper will decrease
(c) the resistance of copper will increase while that of germanium will decrease
(d) the resistance of copper will decrease while that of germanium will increase
13. Diamond is very hard because ?
(a) it is covalent solid
(b) it has large cohesive energy
(c) high melting point
(d) insoluble in all solvents
14. The part of the transistor which is heavily doped to produce large number of majority carriers is
(a) emitter
(b) base
(c) collector
(d) any of the above depending upon the nature of transistor
15. An Oscillator is nothing but an amplifier with
(a) positive, feedback
(b) negative feedback
(c)large gain
(d) no feedback
17. When a P-N junction diode is reverse biased the flow of current across the junction is mainly due
(a) diffusion of charge
(b) drift charges
(c) depends on the nature o material
(d) both drift and diffusion of charges
18. Which of the following gates corresponds to the truth table given below?
(a) NAND
(b) OR
(c) AND
(d) XOR
19. Which of the following, when added as an impurity, into the silicon, produces n-type semi conductor
(b) Aluminium
(d) both ‘b’ and ‘c’
20. The current gain for a transistor working as common-base amplifier is 0.96. If the emitter current is 7.2 mA, then the base current is
(c)0.39 mA
(d) 0.43 mA
21. When a n-p-n transistor is used as an amplifier then ?
(a) the electrons flow from emitter to collector
(b) the holes flow from emitter to collector
(c) the electrons flow from collector to emitter
(d) the electrons flow from battery to emitter
22. When arsenic is added as an impurity to silicon, the resulting material is?
(a) n-type semiconductor
(b) p-type semiconductor
(c) n-type conductor
(d) Insulator
23. To obtain a p-type germanium semiconductor,it must be doped with ?
Ans: c
24. A semi-conducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be
(a) A p-n junction
(b) An intrinsic semi-conductor
(c) A p-type semi-conductor
(d) An n-type semi-conductor
25. The transfer ratio beta of a transistor is 50. The input resistance of the transistor when used in the common emitter configuration is 1 kOhm. The peak value of the co current for an A.C. input voltage of 0.01 V peak is ?
(a)100 microA
(b) 0.01 mA
(c)0.25 mA
(d) 500 microA
26. The cause of the potential barrier in a p-n diode is ?
(a) Depletion of positive charges near the junction
(b) Concentration of positive charges near the junction
(c) Depletion of negative charges near the junction
(d) Concentration of positive and negative charges near the junction
27. In forward bias, the width of potential barrier in a p-n junction diode?
(b) decreases
(c) remains constant
(d) first increases then decreases
28. A depletion lay consists of?
(b) protons
(c)mobile ions
(d) immobile ions
29. Which of the following when added acts as an impurity into silicon produced n-type semi
(b) Al
(d) Mg
30. In a junction diode, the holes are due to
(a) protons
(b) extra electrons
(c) neutrons
(d) missing electrons
31. The intrinsic semiconductor becomes an insulator at
(c) 300K
(d) —100°C
32. For a common emitter circuit if IC/IE = 0.98 then current gain for common emitter circuit will be
(d) 25.5
33. In a p-n junction
(a) The potential of the p and n sides becomes higher alternately
(b) The p side is at higher electrical potential than the n side
(c) The n side is at higher electrical potential than the p side
(d) Both the p and n sides are at the same potential
34. In the case of a common emitter transistor amplifier the ratio of the collector current to the emitter current Ic/Ie is 0.96. The current gain of the amplifier is ?
(c) 24
(d) 12
35. if a full wave rectifier circuit is operating from 5oHz mains, the fundamental frequency in the
tipple will be
(b) 25Hz
(d) 70.7 Hz
36. A n-p-n transistor conducts when ?
(a) both collector and emitter are negative with respect to, the base
(b) both collector and emitter are positive with respect to the base
(c) collector is positive and emitter is negative with to the base
(d) collector is positive and emitter is at same potential as the base
37. Barrier potential of a p-n junction diode does not depend on?
(a)doping density
(b) diode design
(d) forward bias
38. Reverse bias applied to a junction diode
(a) increases the minority carrier current
(b) lowers the potential barrier
(c) raises the potential barrier
(d) increases the majority carrier current
39. In semiconductors at a room temperature
(a) the conduction band is completely empty
(b) the valence band is partially empty and the conduction band is partially filled
(c) the valence band is completely filled and the conduction band is partially filled
(d) the valence band is completely filled
40. The output of OR gate is 1 when?
(a) if either input is zero
(b) if both inputs are zero
(c) if either or both inputs are 1
(d) only if both inputs are I
41. In a p-n junction photo cell, the value of the photo-electromotive force produced by monochromatic light is proportional to ?
(a) the voltage applied at the p-n junction
(b) the barrier voltage at the p-n junction
(c) the intensity of the light falling on the cell
(d) the frequency of the light falling on the cell
42. Choose the only false statement from the following.
(a) in conductors the valence and conduction bands may overlap.
(b) Substances with energy gap of the order of 10 eV are insulators.
(c) The resistivity of a semiconductor increases with increase in temperature.
(d) The conductivity of a semiconductor increases with increase in temperature.
43. Carbon, Silicon and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C, (Eg)Si and (Eg)Gerespectively. Which one of the following relationship is true in their case?
(a) (Eg)C> (Eg)Si
(b) (Eg)C< (Eg)Si
(c) (Eg)C=(Eg)Si
(d) (Eg)C< (Eg)Ge
44. Application of a forward bias to a p—n junction
(a) widens the depletion zone.
(b) increases the potential difference across the depletion zone.
(c) increases the number of donors on the n side.
(d) increases the electric field in the depletion zone.
45. Zener diode is used for?
(a) Amplification
(b) Rectification
(c) Stabilisation
(d) Producing oscillations in an oscillator
Digital Electronics MCQ
Digital Electronics Test
1.In which of the following base systems is 123 not a valid number?
(a) Base 10
(b) Base 16
(d) Base 3
2. Storage of 1 KB means the following number of bytes
(a) 1000
(d) 1064.
3. What is the octal equivalent of the binary number:
(c) 572
(d) 573.
4. Pick out the CORRECT statement:
(a) In a positional number system, each symbol represents the same value irrespective of its position
(b) The highest symbol in a position number system as a value equal to the number of symbols in the system
(c) It is not always possible to find the exact binary
(d) Each hexadecimal digit can be represented as a sequence of three binary symbols.
5.The binary code of (21.125)10 is
(a) 10101.001
(b) 10100.001
(c) 10101.010
(d) 10100.111.
6.A NAND gate is called a universal logic element because
(a) it is used by everybody
(b) any logic function can be realized by NAND gates alone
(c) all the minization techniques are applicable for optimum NAND gate realization
(d) many digital computers use NAND gates.
7. Digital computers are more widely used as compared to analog computers, because they are
(a) less expensive
(b) always more accurate and faster
(c) useful over wider ranges of problem types
(d) easier to maintain.
8. Most of the digital computers do not have floating point hardware because
(a) floating point hardware is costly
(b) it is slower than software
(c) it is not possible to perform floating point addition by hardware
(d) of no specific reason.
9. The number 1000 would appear just immediately after
(a) FFFF (hex)
(b) 1111 (binary)
(c) 7777 (octal)
(d) All of the above.

10. (1(10101)2 is
(a) (37)10
(b) ( 69)10
(c) (41 )10
(d) — (5)10
11. The number of Boolean functions that can be generated by n variables is equal to
(a) 2n
(b) 2n
(c) 2n-1
(d) — 2n
12. Consider the representation of six-bit numbers by two’s complement, one’s complement, or by sign and magnitude: In which representation is there overflow from the addition of the integers 011000 and 011000?
(a) Two’s complement only
(b) Sign and magnitude and one’s complement only
(c) Two’s complement and one’s complement only
(d) All three representations.
13. A hexadecimal odometer displays F 52 F. The next reading will be
14. Positive logic in a logic circuit is one in which
(a) logic 0 and 1 are represented by 0 and positive voltage respectively
(b) logic 0 and, -1 are represented by negative and positive voltages respectively
(c) logic 0 voltage level is higher than logic 1 voltage level
(d) logic 0 voltage level is lower than logic 1 voltage level.
15. Which of the following gate is a two-level logic gate
(a) OR gate
(b) NAND gate
(d) NOT gate.
16. Among the logic families, the family which can be used at very high frequency greater than 100 MHz in a 4 bit
synchronous counter is
(b) CMOS
17. An AND gate will function as OR if
(a) all the inputs to the gates are “1”
(b) all the inputs are ‘0’
(c) either of the inputs is “1”
(d) all the inputs and outputs are complemented.
18. An OR gate has 6 inputs. The number of input words in its truth table are
(c) 64
(d) 128
19. A debouncing circuit is
(a) an astable MV
(b) a bistable MV
(c) a latch
(d) a monostable MV.
20. NAND. gates are preferred over others because these
(a) have lower fabrication area
(b) can be used to make any gate
(c) consume least electronic power
(d) provide maximum density in a chip.
21. In case of OR gate, no matter what the number of inputs, a
(a) 1 at any input causes the output to be at logic 1
(b) 1 at any input causes the output to be at logic 0
(c) 0 any input causes the output to be at logic 0
(d) 0 at any input causes the output to be at logic 1.
22. The fan put of a 7400 NAND gate is
23. Excess-3 code is known as
(a) Weighted code
(b) Cyclic redundancy code
(c) Self-complementing code
(d) Algebraic code.
24. Assuming 8 bits for data, 1 bit for parity, I start bit and 2 stop bits, the number of characters that 1200 BPS communication line can transmit is
(a)10 CPS
(b)120 CPS
(c) 12CPS
(d) None of the above.
25. Indicate which of the following three binary additions are correct?
1.1011 + 1010 = 10101
II. 1010 + 1101 = 10111
III. 1010 + 1101 = 11111
(a) I and II
(b) II and III
(c) III only
(d) II and III
lectronics: unsolved Multiple Choice Questions on Basis Digital Electronics
MCQ QUIZ Sample test on
Flip Flops
Basics of Digital Gates
Hardware Families like IIL TTl CMOS
Combinational Circuits
Sequential Circuits
Propagation Delay
1. A 1 msec pulse can be converted into a 10 msec pulse by using
(a) an stable multivibrator
(1) a monostable multivibrator
(c) a bistable multivibrator
(d) flip-flop
2. The fastest mode of data transfer from CPU to memory in a microprocessor is
(a) memory mapped I/O
(b) I/O mapped I/O
(c) Interrupt driven I/O
(d) DMA
3. Flat top sampling of baseband signals leads to
(a) aliasing
(b) aperture effect
(c) under-sampling
(d) impossible reconstruction.
4. How many steps are there in the output of10-bit D/A converter?
(a) 1023
(b) 1024
(c) 10
(d) 100
5. Which one of the following can be used to change data from spatial code to temporal code?
(a) Shift registers
(b) Counters
(c) A/D converters
(d) Combinational Circuits
6.For a six bit ladder D/A converter which has digital input of 101001, the analog value is
(assume 0 = 0 Vand 1 = + 10 V)
(a) 0.423
(b) 0.522
(c) 0.641
(d) 0.923
7.Which one of the following is a D to A conversion technique?
(a) Successive approximation
(b) Weighted resistor technique
(c) Dual slope technique
(d) Single slope technique
8.If the memory chip size is 256 x l bits, then the number of chips required to
make up 1K (1024) bytes of memory is
9.Which of the following statements are correct?
1. A flip-flop is used to store 1-bit of information
2. Race-around condition occurs in a J-K flip-flop when both the inputs are 1.
3. Master-slave configuration is used in flip-flops to store 2-bits of information.
4. A transparent latch consists of a D-type flip-flop.
10, The greatest negative number which can be store in a computer that has 8-bit word length and uses 2’s complement arithmetic is
(a) -256
(c) – 128
(d) – 127
11. A retriggerable monoshot is one which
(a) can be triggered only once
(b) has two quasi-stable states
(c) cannot be triggered until full pulse has been outputted.
(d) is capable of being triggered while the output is being generated.
12. A carry look ahead adder is frequently used for addition because, it
(a) is faster
(b) is more accurate
(c) uses fewer gates
(d) costs less
13. When signed numbers are used in binary arithmetic, then which one of the following notations would have unique representation for zero? -
(a) Sign-magnitude
(b) l’s complement
(c) 2’s complement
(d) 9’s complement
14. The number of switching function of 3variables is
(c) 128
(d) 256
15. The gate whose output is LOW if and only if all the inputs are HIGH, is
(c) OR
(d) AND
16. In computer terminology 1 M Byte memory means
(a) 1000000 bytes
(b) 1000024 bytes
(c) 1024000 bytes
(d) 1048576 bytes
17. A unit pulse input is given to a single-pole stable digital filter. Its output response will be?
(a) constant pulses
(b) exponentially decaying pulses
(c) impulse
(d) exponentially rising pulses
18. The number of flip flops required in a decade counter is
(a) 2
(b) 3
(c) 4
(d) 10
19. A square wave with a period of 10 micro sec drive a flip flop. The period of.the output signal.will be
(a)100 micro sec
(b)20 micro sec
(c) 10 micro sec
(d) 5 micro sec
20.A digital Voltmeter has 4 and 1/3 digits display .The 1 volt range can read upto
(b) 1.1111
(d) 19999
21. Ultraviolet radiations are used in IC fabrication process for? -
(a) diffusion
(b) masking
(c) isolation
(d) metallization
22. In PCM system if the quantization levels are increased from 2 to 8, the relative bandwidth requirement will
(a) remain same
(b) be doubled
(c) be tripled
(d )be four times
23. The 7-bit Hamming code (even parity check) 001 for a BCD digit is known to have a single error. Therefore, encoded BCD digit is
(a) 9
(b) 5
(c) 3
(d) 0
24. If NxN = (7601 ) where N is a positive integer, then the value of N is
(a)(241)base 5
(b)(143) base 6
(c)(165)base 7
(d)(39)base 16
25. The input-output equation of a system is given by
y(n)=x(n) square
where y(n) and x(n) represent output , input sequences respectively. The system is
(a) linear and causal
(b) linear and noncausal
(c) nonlinear and causal
(d) nonlinear and noncausal.
26. The number of comparators required to build a 5-bit Analog to Digital Converter (ADC)is
(a) 5
(b) 11
27. A 555 timer can be used as
(a) an astable multivibrator only
(b) a monostable multivibrator only
(c) a frequency divider only
(d) an astable multivibrator or a monostable muttivibrator or a frequency divider
28. A synchronous sequential circuit is to be designed which will produce an output ‘1’ when previous two and present input represent an even number, with present input being least significant bit. The minimum number of states of the machine will be
(c) 4
29. The specification for a standard 74 series TFL gate reads propagation delay as 35 ns and power dissipation as I mW. This circuit is
(a) high speed TTL
(b) low power TTL
(c) standard Schottky TTL
(D) low power Schottky TTL
Directions : The following question consists of two statements, one labelled as the ‘Assertion (A) ‘and the other as ‘Reason (R) “. You are to examine these two statements carefully and select the answer’ to this question using the code given below.
Assertion (A) The modernization process has challenged the hold caste system in India.
Reason (R) Mobility as a phenomenon of change in caste system does not challenge the basic structure of caste.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true, but R is not the correct explanation of A
(c) A is true, but R is. false
(d) A is false, but R is true
Assertion (A):A programmable Read only-Memory can be used as a synchronous counter
Reason (R) : Each memory location of a programmable Read- Only-Memory is programmable and can be read synchronously.
30. Assertion (A): Master slave f flip flop is commonly employed in high speed synchronous circuitry.
Reason (R) It uses two JK flip flops in cascade.
31. Assertion (A) : A demultiplexer cannot be used as a decoder.
Reason (R): A demultiplexer selects one of many outputs whereas a decoder selects an output corresponding to the coded input.
32. Assertion (A) : In analog computation only summing amplifiers and integrators
Reason (R) : The differentiators using operational amplifiers cannot be designed.
33.Assertion (A) : Self-biasing is generally used for a CE amplifier
Reason (R) : The design of self-biasing circuit is very easy as compared to other
34. Assertion (A) : 2’s complement arithmetic is preferred in digital computers
Reason (R) : To obtain the 2’s complement of a number, the hardware required is simple.
35. Assertion (A): XOR gate is not a universal gate.
Reason (R) : It is not possible to realize any Boolean function using XOR gates only.
36.Assertion (A) : ECL gate has the highest speed of operation
Reason (R) : The transistors in ECL gate operate in the active region.
37. Assertion (A) : The basic operation of a micro-processor consists of fetching and execution of instructions one by one
Reason (R) The instruction set of a microprocessor is stored inside the ALU
38. Assertion (A) In a heterodyne digital counter, the input signal is heterodyned to a lower frequency
Reason (R) The gating and counting circuits of a digital counter cannot handle GHz signals.
39. Assertion (A) Dual-slope A/D converter is the most preferred A/D conversion approach in digital multimeters.
Reason (R) Dual-slope A/D converter,provides high accuracy in A/D conversion while at the same time
suppressing the hum effect on the input signal.
40. Assertion (A) A digital multiplexer can also be used to implement combinational logic function
Reason (R) In a combinational circuit, the current output depends on the previous outputs also.
41. Assertion (A) The sampled data system with its characteristic equation
Z2- 4z + 4 = 0 is unstable
Reason (R) : Sampled data systems with positive roots of the characteristic equation are unstable.
42. Assertion (A) Fast events can be captured and displayed by a real-time spectrum analyzer.
Reason (R) All components of a signal are presented simultaneously in the frequency domain. In swept type spectrum analyzer, frequencies are supplied one at a time at a particular rate.
43. Assertion (A) Among RAM and ROM, ROM is used as firmware memory
Reason (R) ROM can be accessed for alteration.
Unsolved Basic Digital Electronics  Quiz
MCQ on Fundamentals of Digital Electronics
Digital Electronics Exam (Quiz)
Multiple Choice Questions on Digital Electronics
Digital Electronics Practice Sample Test For Graduate Engineer /Management Trainee Jobs in
DD and AIR
UPSC Civil Services
1. Humming codes are used for error detection and correction. If the minimum Hamming distance is m, then the number of errors correctable is ?
(a) equal to m
(b) less than m/2
(c) equal to 2 m
(d) greater than m.
2. Which be-of the following is equivalent to AND-OR realization?
(a)        NAND-NOR realization
(b)        NOR-NOR realization
(c)        NOR-NAND realization
(d)        NAND-NAND realization
3. The figure of merit of a logic family is Given  by
(a)        gain bandwidth product
(b) (propagation delay time) x (power dissipation)
(c)        (fan-out) x (propagation delay time)
(d)        (noise margin) x (power dissipation).
4. Logic gate HTL is characterized by
(a). High fan-out
(b) Highest speed of operation
(c). High noise immunity
(d)Lowest product of power and delay
5. Logic gate CMOS  is characterized by
(a). High fan-out
(b) Highest speed of operation
(c). High noise immunity
(d)Lowest product of power and delay
6. Logic gate IIL is characterized by
(a). High fan-out
(b) Highest speed of operation
(c). High noise immunity
(d)Lowest product of power and delay

7. Logic gate ECL is characterized by
(a). High fan-out
(b) Highest speed of operation
(c). High noise immunity
(d)Lowest product of power and delay
8. A combinational circuit is one in which the output depends on the
(a) input combination at that time
(b) input combination and the previous output
(c) input combination at that time and the previous input combination
(d) present output and the previous output.
9.Which one of the following will give the sum of full-adder as output?
(a) Three input majority circuit
(b) Three bit parity checker
(c) Three bit comparator
(d) Three bit counter.
10. A full-adder can be implemented with half-adders and OR gates. A 40 bit parallel full adder without any initial carry
requires            -
(a)        8 half-adders, 4-OR gates
(b)        8 half-adders, 3-OR gates
(c)        7 half-adders, 4-OR gates
(d)        7 half-adder, 3-OR gates.
11. In a sequential circuit, the outputs at any instant of time depend
(a) only on the inputs present at that instant of time
(b) on past outputs as well as present. inputs
(c) only on the past inputs
(d) only on the past outputs.
12..The Q output of a J-K FLIP-FLOP is ‘1’.
The output does not change when a clock-pulse is applied. The inputs j and K
will be respectively (where x — don’t care state)
(a) 0 and x
(b) x and 0
(c)1 and 0
(d)0 and 1
13.A    4-bit synchronous counter uses flip-flops with propagation delay time of 15ns each. The maximum possible time
required for change. of state will be
(a) l5ns
(b) 30ns
(c) 45ns
14 A divided by 78 counter can be realized by using
(a) 6 nos of mod-13 counters
(b) 13 nos of mod-6 counters
(c) one .mod-13 counter followed by one mod-6 counter
(d) 13 nos of mod-13 counters.
15. The disadvantage of a counter-type A/D converter as compared to comparator type AID converter is that
(a) the resolution is low
(b) longer conversion time is required
(c) the circuitry is more complex
(d) its stability is low.
16. Flash ADC is
(a) a serial ADC
(b) a parallel ADC
(c) partly serial and partly parallel ADC
(d) a successive approximation ADC.
17.In a 4-bit weighted  D/A converter, the resistor value corresponding to LSB is 32 k Ohms  The resistor value corresponding to MSB will be
(a)32k Ohms
(b) l6k Ohms
(c)8k Ohms
(d)4k Ohms
18. A 10-bit D/A converter provides an analog output which has a maximum value of 10.23 volts. The resolution is
(a) l0 mV
(b)20 mV
(c)15 mV
(d) 25 mV.
19. The microprocessor system communicates with peripherals via?
(a) read only memories
(b) input and output ports
(c) the address bus
(d) a keyboard
20. ROMs are used primarily for:
(a) data storage
(b) temporary programme and data storage
(c) they are inexpansive
(d) permanent program and data storage.
21 Hexadecimal is preferred over decimal when working with binary numbers because.
(a) hex is easier for people to use
(b) hex gives a less compact representation
(c) hex has a simpler relationship to binary
(d)decimal has a simpler relationship to binary.
22. One advantage of the microprocessor based operation over a standard wiredd logic operation is that
(a) It is faster
(b) It is easier to modify
(c) The hardware is simpler.
(d) It uses less power.
23. A microprocessor based system can perform many different functions because
(a) Its operation is controlled by software
(b) it is digital system
(c) It uses a RAM
(d) It can be controlled by an input and output devices.
24. The accumulator’s main purpose is
(a) temporary data storage
(b) keeping track of the next instruction to be executed -
(c) selecting which peripheral should be addressed
(d) storing instructions.
25. The program counter is used for
(a) data storage
(1b) instruction storage
(c) storing the address of the instruction waiting to be executed
(d) counting programs.
26. The nurnber of machine cycles required to execute an instruction depends upon
(a) the number or bytes inthe instruction
(b) the clock period
(c) the type of instruction
(d) none of the above.
27. The purpose of the ALU is to
(a) interpret the opcodes
(b) perform arithmetic and logic operations
(è) control the address bus
(d) calculate the number of machine cycles required.
28. The data bus is
(a) unidirectional and three-state
(b) bi-directional and three state
(c) unidirectional and bi-directional
(d) none all of the above.
29. Devices in a microprocessor system
(a) have specific addresses assigned to them
(b) always respond to only single address
(c) are always controlled by an address decoder circuit
(d) are all of the above.
30. The main advantage of dynamic RAMs over static RAMs is that they are
(a) non-volatile
(b) easier to use
(c) less expensive
(d) all of the above.
31. Dynamic RAMs are best suited to
(a)slow systems
(b) small systems
(c)large systems
(d) one-bit systems.
32. The program ROM found in high volume microprocessor-based product most likely to be a;
(a)mask ROM
(b) PROM
(d) EAROM.
33. All microprocessor systems need peripherals to
(a) interact with the outside world
(b) supply data to the microprocessor
(c) receive data from the microprocessor all of the above.
(d) all of the above.
34. A Firmware is
(a) another name of software
(b) a special type of hardware used in a microprocessor based system
(c) a program stored in a ROM
(d) a program written in a EAROM.
35. The language that a computer understand is
(a) assembly language
(b) machine language
(d) none of the above.
36. In a Top-down software design approach, the smallest program modula  is
(a) A sub-routine
(to) Functional program/Unit
(c) Executive
(d) None of the above.
37. Man-machine language is
(a) a high level language
(b) a special language for communication between a man and a machine
(c) software to communicate with the computer  peripherals
(d) none of the above.
38. If the various logic families are arranged in the ascending order of their fan-out capabilities, the sequence will be
39. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either
(a) aNAND or an EX-OR
(b) an OR or an EXNOR
(c) an AND or an EX-OR
(d) a NOR or an EX-NOR
40 Which one of the following sets of gates are best suited ‘for parity checking and parity generation?
(a) AND, OR, NOT gates
(b) EX-OR or EX-NOR gates
(c) NAND gates
(d) NOR gates
41 Two’s complement of a given 3 or more bit binary number of non-zero magnitude is the same as the original number if all
bits except the
(a) M5B are zeros
(b) LSB are zeros
(c) MSB are ones
(d) LSB are ones
42.The race-around condition is NOT present in
(a) RS flip-flop
(to) JK flip-flop
(c) D flip-flop
(d) Master Slave flip-flop.
43.Which of the following characteristics are necessary for a sequential circuit?
1.         It must have at least six gates
2.         It must have some feedback.
3 Its output should depend on sonw past value.
Select the correct answer using the codes given below:
(a) 1,2 and 3
(b) 1 and 2
(c) 2 and 3
(d) l and 3.
44.Which one / of the microprocessor has refresh logic for  dynamic memory?
(a) 6502
(b) INTEL 8085
(c) Motorola MC 6800
(d) Z80
45 .In hexadecimal system, 77 — 3B is equal to
46.Which one of the following statements is true of SP register in  8086 microprocessor?
(a) It can be used for reading instruction from memory
(b) The result of arithmetic operation always goes to SP
(c) It can be used for reversing the string
(d) The control command first goes to SP
47. The noise margin of a digital IC is the
(a) maximum frequency of extraneous voltage that does not cause a gate to change its state
(b) maximum extraneous voltage that does not cause a gate to change its state
(c) thermal noise voltage which causes a gate to change its state
(d) minimum frequency of extraneous voltage that causes a gate to change its state
48. The most economical manner in which a high-speed decade counter can be realized is by using
(a) synchronous binary counter
(b) ripple binary counter
(c) ring counter
(d) Johnson counter
49. If it is desired to have a 64 x 8 memory and if the memories available are of
16 x 4 size, then the number of memories required will be
50. The register which keeps track of the sequence of instruction execution is?
(a) memory address register
(b) memory buffer register
(c) stack pointer
(d) program counter

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