12th class Physics unit 7 MCQs
26. A diode characteristics curve is a plot between:
a. Voltage and current
b. Current and resistance
c. Current and time
d. Voltage and time
27. The gain of transistor amplifier depends upon:
a. Input voltage
b. Resistance connected with collector
c. Output voltage
d. Resistance connected with base voltage
28. Greater concentration of impurity is added in:
a. Collector
b. Base
c. LED
d. Emitter
29. The value of potential barrier for silicon at room temperature is:
a. 0.3 V
b. 0.7 V
c. 0.9 V
d. 0.5 V
30. Minimum number of semi-conductor diodes required for full wave rectification are:
a. 3
b. 1
c. 4
d. 2
31. The open loop gain of the amplifier is order of:
a. 105
b. 102
c. 1012
d. 108
32. The device which is used as amplifier and works with the negative feedback is:
a. p-n-p transistor
b. Operational amplifier
c. Transistor
d. n-p-n transistor
33. The gain of Amplifier is given as:
a. -R2/R1
b. -βRc /rlc
c. 1+ R2/R1
d. βrlc / Rc
34. The number of diodes in bridge rectifier is:
a. 2
b. 4
c. 5
d. 3
35. During negative half cycle of A.C then p-n junction offers:
a. No resistance
b. High resistance
c. Low resistance
d. All of these
36. Output resistance of an op-amp is:
a. Low
b. High
c. Equal to input resistance
d. Zero
37. The input resistance of an op-amplifier is:
a. High
b. Zero
c. Equal to output resistance
d. Low
38. For rectification we use:
a. Choke
b. Transformer
c. Generator
d. Diode
39. The output voltage of a rectifier is:
a. Perfectly direct
b. Smooth
c. Alternating
d. Pulsating
40. Find the gain of inverting amplifier of external resistance R1 = 10KΩ and R2 100KΩ .
a. -2
b. -5
c. 50
d. -10
41. Pulsating output of full wave rectifier can be made smooth by using circuit called:
a. Resistor
b. Filter
c. Transistor
d. Amplifier
42. A device used for the conversion of A.C into D.C is called:
a. An amplifier
b. An oscillator
c. Rectifier
d. Detector
43. For non-inverting amplifier if R1 = ∞ohm, R2= 0 ohm then gain of amplifier is:
a. +1
b. -1
c. 0
d. infinite
44. LDR becomes necessary when op-amp as a:
a. Rectifier
b. Night switch
c. Comparator
d. Inverter
45. Rectification is the process of converting:
a. Low signal to high
b. D.C into A.C
c. High signal to low
d. A.C into D.C
46. In full was rectification number of diodes required are equal to:
a. 5
b. 4
c. 1
d. 3
47. The use of LDR is in the circuit of:
a. Rectifier
b. High switch
c. Oscillator
d. Logic gate
48. Automatic functioning of street lights can be done by the use of:
a. Comparator
b. Inductor
c. Emf
d. Rectifier
49. In photovoltaic cell, current is directly proportional to:
a. Frequency of light
b. Wavelength of light
c. Energy
d. Intensity of light
50. Which is not a basic logic operation?
a. OR
b. NOT
c. NAND
d. AND