For transistor action:

Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)                                       
4. (c) and (d)

The emitter-base junction of a transistor is …… biased while the collector-base junction is ……. biased.
1. reverse, forward                       

2. reverse, reverse

3. forward, forward                       

4. forward, reverse

When a transistor is used in a common emitter mode as an amplifier:

In an amplifier, an npn-transistor is used in common-emitter mode. If $\beta$ =25, then what will be the collector current if emitter current is 13 mA?

1. 13.5 mA

2. 12.5 mA

3. 11 mA

4. 10.5 mA

In an NPN transistor, 10⁸ electrons enter the emitter in ${10}^{-8}$s. If 1% electrons are lost in the base, the fraction of current that enters the collector and the current amplification factor are, respectively:

1. 0.7 and 50

2. 0.9 and 90

3. 0.8 and 49

4. 0.99 and 99

In an NPN transistor amplifier, if 98% of electrons emitted from the emitter reach the collector, then the value of collector current for the base current of 40 $\mu$A will be:

1. 1.96 mA             

2. 1.92 mA             

3. 1.96 A             

4. 1.92 A

In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current?
1. 50 $\mathrm{\mu }$A 
2. 100 $\mathrm{\mu }$A
3. 150 $\mathrm{\mu }$A 
4. 200 $\mathrm{\mu }$A

Consider an NPN transistor amplifier in the common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?
1. 1.1 mA                     

2. 1.01 mA

3. 0.01 mA                   

4. 10 mA

An NPN transistor conducts when: