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NUMS T9 Electronics & Dawn of modern physics

Total questions: 100

Worksheet time: 2hrs 38mins

Name
Class
Date
1.

Efficiency of half wave rectifier is

a)

30%

b)

90%

c)

50%

d)

40%

2.

In half wave rectification, the output DC voltage is obtained across the load for:

a)

The positive half cycle of input AC

b)

The negative half cycle of input AC

c)

The positive and negative half cycles of input AC

d)

Either positive or negative half cycle of input AC

3.

A component that allow only unidirectional current to pass through is

a)

resistor

b)

diode

c)

transformer

d)

inductor

4.

Output voltage of rectifier is not smooth; it can be made by a circuit known as:

a)

Wheat stone circuit

b)

Filter circuit

c)

Bridge circuit

d)

Ripple circuit

5.

A pn junction (D. shown in the figure can act as a rectifier. An alternating current source (V) is connected in the circuit. The output current in the circuit is represented by:

a)
b)
c)
d)
6.

half wave rectifier, the output voltage is taken across_______

a)

Diode

b)

Resistor

c)

Input voltage

d)

Capacitor

7.

In a half wave rectifier, the current through load resistance flows only in

a)

Positive half cycle

b)

Both half cycles

c)

Negative half cycle

d)

One half cycle

8.

The most common device used as filter is

a)

Transformer

b)

Capacitor

c)

Resistor

d)

Transistor

9.

Output of half wave rectifier is suitable only

a)

To operate radio

b)

Charging batteries

c)

For running a D.C motor

d)

All of these

10.

In the given figure the current through the resistor is practically.

a)

1 A

b)

Zero

c)

2 A

d)

5 A

11.

In the following figure what happens for the positive half cycle of the input

a)

D4 and D3 conducts

b)

D1 and D2 conducts

c)

D4 and D2 conducts

d)

D1 and D3 conducts

12.

For single phase supply frequency of 50 Hz, ripple frequency in full wave rectifier is

a)

25 Hz

b)

100 Hz

c)

50 Hz

d)

200 Hz

13.

an half wave rectifier, the input sine wave is 250sin100 pt. The output ripple frequency of rectifier will be

a)

50Hz

b)

100Hz

c)

200Hz

d)

25Hz

14.

Rectifier allows unidirectional current through load during entire 360° of input cycle is

a)

Half wave rectifier

b)

Capacitor

c)

Full wave rectifier

d)

Amplifier

15.

semi-conductor can be used as a rectifier because

a)

It has low resistance to the current flow when forward biased

b)

It has low resistance to the current flow when forward biased and high resistance when reversed biased

c)

It has low resistance to the current flow when reversed biased

d)

None of above

16.

A half wave rectifier is being used to rectify an alternating voltage of frequency 5O Hz. The number of pulses of rectified current obtained in one second is:

a)

50

b)

100

c)

25

d)

200

17.

Which circuit is used for the smooth output voltage in rectification?

a)

Oscillator

b)

Rectifier

c)

Filters

d)

Amplifier

18.

How many diodes are used for the full wave rectification in bridge rectifier:

a)

Two

b)

Four

c)

Three

d)

Five

19.

If an AC voltage of 100V peak value is applied as input to a half wave rectifier and then a full wave rectifier, the rms values of outputs will be respectively

a)

35V and 35V

b)

35V and 70V

c)

50V and 70V

d)

70V and 140V

20.

In a bridge full wave rectifier, the input sine wave is 250sin 100 t. The output ripple frequency will be:

a)

50Hz

b)

100Hz

c)

200Hz

d)

25Hz

21.

When p-n junction diode is forward biased

a)

The depletion region is reduced and barrier height is increased

b)

The depletion region is widened and barrier height is reduced

c)

Both the depletion region and barrier height reduced

d)

Both the depletion region and barrier height increased.

22.

The resistance of an ideal diode in reverse bias condition is

a)

Infinite

b)

Finite

c)

Zero

d)

Negative

23.

Which one is reverse-biased?

a)
b)
c)
d)
24.

A semi-conductor can be used as a rectifier because

a)

It has low resistance to the current flow when forward biased

b)

It has low resistance to the current flow when reversed biased

c)

It has low resistance to the current flow when forward biased and high resistance when reversed biased

d)

None of above

25.

If peak Voltage across a full wave rectifier is 20V then Vrms is

a)

7.07

b)

14.14

c)

16.8V

d)

12V

26.

A full wave rectifier passes ___________into positive cycles

a)

lower half cycles

b)

upper half cycle

c)

both cycles

d)

none of them

27.

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kΩ. Calculate the fraction of the cycle during which the diode is conducting

a)

4.82%

b)

3.18 %

c)

2.06%

d)

1.06 %

28.

A half wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be

a)

100 Hz

b)

25 Hz

c)

200Hz

d)

50Hz

29.

In a half wave rectification, the diode conducts during

a)

both half cycles

b)

positive half

c)

negative half

d)

none of these

30.

Ripple factor of half wave rectifier is

a)

1.21

b)

0.8

c)

0.6

d)

0.4

31.

If the line frequency is 50 Hz, the output frequency of bridge rectifier is

a)

50Hz

b)

100Hz

c)

200Hz

d)

150Hz

32.

In a Centre tap full wave rectifier if Vm is the peak voltage across the secondary of transformer, the maximum voltage across reverse bias is

a)

Vm

b)

Vm/√2

c)

2Vm

d)

Vm/3

33.

Transformer is used in rectification to ______the supply voltage

a)

step up

b)

step down

c)

equalizes

d)

none of them

34.

Which of the following rectifier uses wheatstone bridge to rectify signal?

a)

half wave

b)

full wave

c)

bridge

d)

All of the above

35.

The process of converting alternating current to direct current is called

a)

modulation

b)

amplification

c)

oscillation

d)

rectification

36.

If a half wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in rectifier voltage is:

a)

25

b)

50

c)

100

d)

75

37.

The maximum efficiency of full wave rectifier is

a)

80.60

b)

40.60%

c)

70%

d)

50%

38.

Ripple factor of full wave rectifier is

a)

1.21

b)

0.6

c)

0.482

d)

0.9

39.

To get a peak load voltage of 40V out of a bridge rectifier, what should be the approximate rms value of secondary voltage?

a)

0V

b)

14.4V

c)

28.3V

d)

56.6 V

40.

The output voltage of a rectifier is

a)

smooth

b)

perfectly direct

c)

alternating

d)

pulsating

41.

Average dc Voltage across the load in terms of Vmax is

a)

0.532 Vmax

b)

0.637Vmax

c)

0.759Vmax

d)

0.437Vmax

42.

Which of the following is not a type of rectifier?

a)

Phase wave rectifier

b)

Full wave

c)

half wave

d)

none of them

43.

The bridge rectifier is preferred to an ordinary two diode full wave rectifier because

a)

it needs much smaller transformer for the same output

b)

no center tap required

c)

less PIV rating per diode

d)

All of the above

44.

Which of the following is a type of rectifier:

a)

half wave

b)

full wave

c)

bridge

d)

All of the above

45.

Half wave voltage multiplier can provide any degree of voltage multiplication by cascading diodes and capacitors.

a)

any doubler

b)

any tripler

c)

any multiplication

d)

none of them

46.

A capacitor is to be used to provide smoothing for a half wave rectifier. In which of the following diagrams is capacitor correctly connected?

a)

A

b)

B

c)

C

d)

D

47.

In Fig. the input is across the terminals "A" and "C" and the output is across "B" and "D" Then the output is:

a)

half wave rectified

b)

full wave rectified

c)

same as the input

d)

zero

48.

In the bridge rectifier when "Vi" is positive at point "A" with respect to "B" which diodes are ON.

a)

D2 and D4

b)

D2 and 03

c)

D1 and D3

d)

D1and 04

49.

During the 0 to T/2 the forward biased diode offers

a)

Very small resistance

b)

Very high resistance

c)

Very small current flow through it

d)

Zero resistance

50.

No of diode in center tap full wave rectifier

a)

4

b)

2

c)

1

d)

3

51.

Which region of the electromagnetic spectrum will provide photons of the least energy

a)

X-ray

b)

Infrared light

c)

Radio waves

d)

Ultra violet light

52.

What is a quantum of light called?

a)

Electron

b)

Photon

c)

Neutron

d)

Proton

53.

Why are photons of gamma rays and X-rays able to penetrate objects more successfully than ultraviolet radiation?

a)

Photons of gamma rays and X-rays carry with them less energy

b)

Photons of gamma rays and X-rays have longer wavelengths

c)

Photons of gamma rays and X-rays have lower frequencies

d)

Photons of gamma rays and X-rays carry with them more energy

54.

In photoelectric effect, electrons are ejected from metals, if the incident light has a certain minimum

a)

Wavelength

b)

Frequency

c)

Amplitude

d)

Angle of incidence

55.

The momentum of photon is

a)

h/c

b)

hc/lamda

c)

h/lamda

d)

Both b and c

56.

The wavelength of light beam B is twice the wavelength of light beam B. The energy of a photon in beam A is:

a)

Half the energy of a photon in beam B

b)

One-fourth the energy of a photon in beam B

c)

Equal to the energy of a photon in beam B

d)

Twice the energy of a photon in beam B

57.

The wave theory of light does not explain

a)

Diffraction

b)

Photocurrent

c)

Polarization

d)

Interference

58.

A photon in light beam A has twice the energy of a photon in light beam B. The ratio pA/pB of their momenta is:

a)

4

b)

1/4

c)

2

d)

1/2

59.

Which one has the largest wavelength when all of the following moving with the same speed

a)

An electron

b)

A proton

c)

An alpha-particle

d)

All have same de-Broglie wavelength

60.

If momentum of a particle is doubled then de-Broglie wavelength become

a)

Double

b)

Half

c)

Unchanged

d)

Four times

61.

During the Davisson-Germer experiment what was proved

a)

Particle nature of light

b)

Wave nature of particle

c)

Both A and B

d)

None

62.

The particle nature of light is not confirmed by

a)

Photoelectric effect

b)

Diffraction of light

c)

Scattering of X-rays by electrons

d)

Compton effect

63.

Electrically, photons are

a)

Positively charged

b)

Negatively charged

c)

Neutral

d)

Strongly charged, may be positive or negative

64.

photon is ____________

a)

unit of energy

b)

positively charged particle

c)

quantum of electromagnetic radiation

d)

unit of wavelength

65.

Frequency of photon having energy 66 eV is

a)

8 × 10-15Hz

b)

16 × 1015Hz

c)

12 × 10-15Hz

d)

None of these

66.

If the energy of the photon is increased by a factor of 4, then its momentum

a)

Does not change

b)

Increases by a factor of 4

c)

Decreases by a factor of 4

d)

Decreases by a factor of 2

67.

Of the following properties, the photon does not possess

a)

Momentum

b)

Energy

c)

Rest mass

d)

Frequency

68.

In Compton scattering from stationary electrons the largest change in wavelength occurs when the photon is scattered through

a)

0°

b)

90°

c)

180°

d)

45°

69.

Which one has the largest wavelength when all of the following moving with the same speed?

a)

An electron

b)

A proton

c)

An a-particle

d)

All have same de-Broglie wavelength

70.

When light is incident on a metal surface the maximum kinetic energy of emitted electrons

a)

Vary with intensity of light

b)

Vary with frequency of light

c)

Vary with speed of light

d)

Vary irregularly

71.

The photoelectric effect is based on the law of conservation of

a)

Momentum

b)

Angular momentum

c)

Mass

d)

Energy

72.

Calculate the energy of a photon of wavelength 6600 angstroms.

a)

0.3 × 10-19J

b)

3× 10-19J

c)

30 × 10-19J

d)

00 × 10-19J

73.

The frequency of light beam A is twice that of light beam B. The ratio EA/EB of photon energies is:

a)

1/2

b)

4

c)

1/4

d)

2

74.

Which of the following electromagnetic radiations has photons with the greatest momentum?

a)

Blue light

b)

Radio waves

c)

Microwaves

d)

X rays

75.

Number of photo electrons depends upon

a)

Frequency of incident light

b)

Energy of incident light

c)

Intensity of incident light

d)

Wavelength of incident light

76.

The work function of a metal is 6.63 eV, its threshold frequency is:

a)

1.6 × 1015Hz

b)

6.63 ×10-34Hz

c)

1.6× 1012 Hz

d)

1.6 ×10-19Hz

77.

If momentum of a particle is doubled then de-Broglie wavelength become

a)

Double

b)

Unchanged

c)

Half

d)

Four times

78.

The experimental value of Rydberg constant is

a)

1.097 ×10-8 m-1

b)

1.097 ×108 m-1

c)

1.097 ×107 m-1

d)

1.097 ×10-7 m-1

79.

The minimum energy required to remove an electron from metal surface is called

a)

Stopping potential

b)

Work function

c)

Kinetic energy

d)

None of these

80.

A photosensitive plate is illuminated by green light and photoelectrons are emitted with maximum kinetic energy 4EV . If the intensity of the incident radiation is reduced to one-fourth of the original value, then the maximum K.E. of the photoelectrons will be

a)

0.1 eV

b)

1 eV

c)

4 eV

d)

16 eV

81.

To detect a signal of radio wave__________ of photons are needed.

a)

One

b)

Few hundred

c)

Infinite no

d)

Millions

82.

The energy of photon of radio waves is only

a)

10-10eV

b)

10-5eV

c)

100 eV

d)

1 MeV

83.

When light falls on the metal surface, the energies of the emitted electrons vary with

a)

speed of light

b)

intensity of light

c)

frequency of light

d)

remain unchanged

84.

photoelectric effect when monochromatic light is allowed to shine on cathode, it begins to

a)

emit electrons

b)

emit protons

c)

absorb electrons

d)

emit neutrons

85.

The work function of a photoelectric material is 3.3 eV. The threshold frequency will be equal to

a)

8×104Hz

b)

8×1056Hz

c)

8×1010Hz

d)

8×1014Hz

86.

The electrons are emitted in the photoelectric effect from a metal surface

a)

Only if the frequency of the incident radiation is above a certain threshold value

b)

Only if the temperature of the surface is high

c)

At a rate that is independent of the nature of the metal

d)

With a maximum velocity proportional to the frequency of the incident radiation

87.

When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then

a)

No electrons are emitted

b)

Photons are emitted

c)

Electrons of lower energy are emitted

d)

Electrons of higher energy are emitted

88.

The work function of aluminium is 4.2 eV. If two photons, each of energy 3.5 eV strike an electron of aluminium, then emission of electrons will be

a)

Possible

b)

Not possible

c)

Data is incomplete

d)

Depend upon the density of the surface

89.

In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of photoelectrons will become

a)

Double

b)

Half

c)

Four time

d)

No change

90.

Radio waves have energy of -10ev. Calculate its frequency.

a)

2.5×104 Hz

b)

2.5 ×105 Hz

c)

3.7×109Hz

d)

5MHz

91.

A wave has wavelength of 1.6×10-10m Calculate energy of wave in ev.

a)

7.6×103 ev

b)

12×10-3 ev

c)

6×102 ev

d)

none of these

92.

Alpha particle and proton is traveling with same velocity.The ratio between their wavelength is:

a)

4:1

b)

1:4

c)

3:1

d)

1:3

93.

Relation between mass and energy

a)

E=mc

b)

E=m/c

c)

E=mc2

d)

none of these

94.

Mass and energy are related to each other by

a)

Newton law

b)

coulombs law

c)

Einstein law

d)

all of these

95.

The existence of positron was discovered in

a)

thermal radiation

b)

cosmic radiation

c)

electromagnetic radiation

d)

non-electromagnetic radiation

96.

Pair production is possible in_____ Photon

a)

X rays

b)

beta rays

c)

gamma rays

d)

all of there

97.

For a wave one them is independent of others:

a)

Amplitude

b)

frequency

c)

wave length

d)

time period

98.

In annihilation process particles move in:

a)

Same direction

b)

opposite direction

c)

Perpendicular direction

d)

None of these

99.

Linear momentum of 3Mev photon is

a)

.01

b)

.02

c)

.03

d)

.04

100.

Frequency of photon whose energy is 66.3 ev

a)

12.6×106Hz

b)

19.6×106Hz

c)

1.6×1015Hz

d)

81.6×106Hz

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