If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be

(1) 50 Hz                           

(2) 70.7 Hz

(3) 100 Hz                         

(4) 25 Hz

A diode having potential difference 0.5 V across its junction which does not depend on current, is connected in series with resistance of 20 $\mathrm{\Omega }$ across source. If 0.1 A passes through resistance then what is the voltage of the source

1. 1.5 V                     

2. 2.0 V

3. 2.5 V                     

4. 5 V

When NPN transistor is used as an amplifier

(1) Electrons move from base to collector

(2) Holes move from emitter to base

(3) Electrons move from collector to base

(4) Holes move from collector to emitter

The phase difference between input and output voltages of a CE circuit is 

(1) 0$°$                         

(2) 90$°$ 

(3) 180$°$                      

(4) 270$°$ 

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

In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector its base current in mA is

1. 36                       2. 26
3. 16                       4. 6

If $\mathrm{\alpha }$ = 0.98 and current through emitter ${\mathrm{i}}_{\mathrm{e}}$ = 20 mA, the value of $\mathrm{\beta }$ is 
(a) 4.9                  (b) 49
(c) 96                   (d) 9.6

In a PNP transistor working as a common-base amplifier, current gain is 0.96 and emitter current is 7.2 mA. The base current is:

(1) 0.4 mA                   

(2) 0.2 mA

(3) 0.29 mA                   

(4) 0.35 mA

 If ${\mathrm{l}}_1$, ${\mathrm{l}}_2$, ${\mathrm{l}}_3$ are the lengths of the emitter, base and collector of a transistor then 
(1)${\mathrm{l}}_1$= ${\mathrm{l}}_2$ = ${\mathrm{l}}_3$                   

(2) ${\mathrm{l}}_3$ <${\mathrm{l}}_2$> ${\mathrm{l}}_1$

(3) ${\mathrm{l}}_3$<  ${\mathrm{l}}_1$ < ${\mathrm{l}}_2$                 

(4) ${\mathrm{l}}_3$> ${\mathrm{l}}_1$>${\mathrm{l}}_2$

In an NPN transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, the emitter current (${\mathrm{i}}_{\mathrm{E}}$) and base current (${\mathrm{i}}_{\mathrm{B}}$) are given by 
(1) ${\mathrm{i}}_{\mathrm{E}}$ = –1 mA, ${\mathrm{i}}_{\mathrm{B}}$ = 9 mA

(2) ${\mathrm{i}}_{\mathrm{E}}$ = 9 mA, ${\mathrm{i}}_{\mathrm{B}}$ = – 1 mA

(3) ${\mathrm{i}}_{\mathrm{E}}$ = 1 mA, ${\mathrm{i}}_{\mathrm{B}}$ = 11 mA

(4) ${\mathrm{i}}_{\mathrm{E}}$ = 11 mA, ${\mathrm{i}}_{\mathrm{B}}$ = 1 mA