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#### 12th Standard Physics Semiconductor Electronics English Medium Free Online Test One Mark questions 2020 - 2021

12th Standard EM

Reg.No. :
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Physics

Time : 00:20:00 Hrs
Total Marks : 20
20 x 1 = 20
1. The barrier potential of a silicon diode is approximately

(a)

0.7 V

(b)

0.3V

(c)

2.0 V

(d)

2.2V

2. The primary use of a zener diode is

(a)

Rectifier

(b)

Amplifier

(c)

Oscillator

(d)

Voltage regulator

3. The light emitted in an LED is due to

(a)

Recombination of charge carriers

(b)

Reflection of light due to lens action

(c)

Amplifi cation of light falling at the junction

(d)

Large current capacity

4. The specific characteristic of a common emitter amplifier is

(a)

High input resistance

(b)

Low power gain

(c)

Signal phase reversal

(d)

Low current gain

5. If the input to the NOT gate is A = 1011, its output is

(a)

0100

(b)

1000

(c)

1100

(d)

0011

6. The output of the following circuit is 1 when the input ABC is

(a)

101

(b)

100

(c)

110

(d)

010

7. Why can't we physically join p-type and n-type semiconductor directly to form a p-n junction?

(a)

Inter-atomic spacing become less than 1 AO

(b)

p -type will repet N-type

(c)

There will be discontinuity for the flowing charge carriers

(d)

Semi-conducting properties will be lost

8. The intrinsic semi-conductor has:

(a)

A finite resistance which does not change with temperature

(b)

Infinite resistance which decreases with temperature

(c)

Finite resistance which decreases with temperature

(d)

Finite resistance which does not change with temperature

9. Which of the following is not the advantage of PN junction diode over tube value?

(a)

Unlimited life

(b)

No warming-up time after switching

(c)

Large efficiency

(d)

Low consumption of power

10. A current gain for, a transistor working as CB amplifier is 0.90. If emitter current is 10 mA, then base current is

(a)

1mA

(b)

2 mA

(c)

0.1 mA

(d)

0.2 mA

11. A N-P-N transistor' conducts when collector is _________ and emitter is ________ with respect to base

(a)

positive, negative

(b)

positive, positive

(c)

negative, negative

(d)

negative, positive

12. In the figure, the input is across A and C output is across Band D. The output is

(a)

same as input

(b)

halfwave rectified

(c)

fullwave rectified

(d)

zero

13. A sinusoidal voltage of peak value 200 volts is connected to diode and resistor R in the circuit shown. If diode is idel, the r.m.s. voltage across R is ________ volt

(a)

100

(b)

$\frac{200}{\sqrt2}$

(c)

200

(d)

280

14. In a N-P-N transistor circuit, the emitter, collector and base current are respectively IE, IC and lB. The relation between them is

(a)

ICEB

(b)

IBCE

(c)

IB>IC>IE

(d)

IB>IC>IE

15. In a common emitter amplifier, output resistance is 5000 Ω and input resistance is 1000 Ω. If peak valueof signal voltage is 1 mV and β =100, than the peak value of output voltage is.

(a)

0.1 V

(b)

0.3 V

(c)

0.2 V

(d)

0.5 V

16. What is output of the combination of the gates shown in the figure below?

(a)

$A+\overline { A.B }$

(b)

A + A.B

(c)

$(A+B).\overline { (A.B) }$

(d)

$(A+B).\overline { (A.B) }$

17. Which of the following figure represents an ideal diode characteristics?

(a)

(b)

(c)

(d)

18. A light emitting diode has a voltage drop of 2v across it when 10 mA current is passed. If this LED is to be operated with 6v battery the value of limiting resistor would be ___________

(a)

400 Ω

(b)

4000 Ω

(c)

40 k Ω

(d)

300 Ω

19. The frequency of output signal of LC oscillator circuit is 100 Hz with capacitance value 0.1μF. IF value of capacitance is taken as 0.2 μF, the frequency of output signal ______________

(a)

decreases by $\frac{1}{\sqrt2}$

(b)

increases by $\frac{1}{\sqrt2}$

(c)

decreases by $\frac12$

(d)

increases by $\frac12$

20. For Boolean identities match the pair
1. $\overset { = }{ A }$ (P) Ā + $\bar { B }$
2. $\overline { A+B }$ (Q) A.B
3. $\overline { A.B }$ (R) $\bar { A } .\bar { B }$
4. A.(Ā + B) (S) A

(a)

1 - (S), 2 (P), 3 - (Q), 4 - (R)

(b)

1 - (S), 2 (R), 3 - (Q), 4 - (P)

(c)

1 - (S), 2 (Q), 3 - (P), 4 - (R)

(d)

1- (S), 2 (R), 3 - (P), 4 - (Q)