A silicon specimen is made into a P-type semi-conductor by dopping, on an average, one Indium atom per $5\times {10}^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5\times {10}^{28} \mathrm{atoms}/{\mathrm{m}}^3$ then the number of acceptor atoms in silicon per cubic centimeter will be:

(1) $2.5\times {10}^{30} \mathrm{atoms}/{\mathrm{cm}}^3$                  

(2) $1.0\times {10}^{13} \mathrm{atoms}/{\mathrm{cm}}^3$

(3) $1.0\times {10}^{15} \mathrm{atoms}/{\mathrm{cm}}^3$                   

(4) $2.5\times {10}^{36} \mathrm{atoms}/{\mathrm{cm}}^3$

The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature

(1) Decreases exponentially with increasing band gap

(2) Increases exponentially with increasing band gap

(3) Decreases with increasing temperature

(4) Is independent of the temperature and the band gap

A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is 

(a) 0.2 A
(b) 0.4 A
(c) Zero
(d) 0.1 A

 In the circuit, if the forward voltage drop for the diode is 0.5V, the current will be 

(a) 3.4 mA
(b) 2 mA
(c) 2.5 mA
(d) 3 mA

Current in the circuit will be 

(a) $\frac{5}{40}\mathrm{A}$
(b) $\frac{5}{50}\mathrm{A}$
(c) $\frac{5}{10}\mathrm{A}$
(d) $\frac{5}{20}\mathrm{A}$

1. \(1.5~\Omega\)
2. \(5~\Omega\)
3. \(6.67~\Omega\)
4. \(200~\Omega\)

In the following common emitter configuration an NPN transistor with current gain $\mathrm{\beta }$ = 100 is used. The output voltage of the amplifier will be 

(1) 10 mV

(2) 0.1 V

(3) 1.0 V

(4) 10 V

A sinusoidal voltage of peak value 200 volts is connected to a diode and resistor R in the circuit shown so that half-wave rectification occurs. If the forward resistance of the diode is negligible compared to R the r.m.s voltage (in volt) across R is approximately

(1) 200                           

(2) 100

(3) $\frac{200}{\sqrt{2}}$                         

(4) 280

The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If ${\mathrm{V}}_{\mathrm{B}}$ = 5 V, then the maximum value of R so that the voltage is above the knee point, will be

(1) 4.3 k$\mathrm{\Omega }$                

(2) 860 k$\mathrm{\Omega }$

(3) 4.3 $\mathrm{\Omega }$                  

(4) 860 $\mathrm{\Omega }$

In the circuit given below, V(t) is the sinusoidal voltage source, voltage drop ${\mathrm{V}}_{\mathrm{AB}}$(t) across the resistance R is

(1) Is half wave rectified

(2) Is full wave rectified

(3) Has the same peak value in the positive and negative half cycles

(4) Has different peak values during positive and negative half cycle