Symbolic representation of four logic gates

are shown as

(i) 

(ii) 

(iii) 

(iv) 

Pick out which ones are for AND, NAND and 

NOT gates, respectively.

1. (iii), (ii)and (i)

2. (iii), (ii) and (iv)

3. (ii), (iv) and (iii)

4. (ii), (iii) and (iv)

If a small amount of antimony is added to germanium crystal

(1) the antimony becomes an acceptor atom

(2) there will be more free electrons than holes in the semiconductor

(3) its resistance is increased

(4) it becomes a p-type semiconductor

In forward biasing of the p-n junction 

In the following figure, the diodes which are forward biased, are

1.  III and IV only

2.  I and III only

3.  II only

4.  II and IV only

A Zener diode, having breakdown voltage equal to \(15\) V, is used in a voltage regulator circuit, as shown in the figure. The current through the diode is:

                      
1. \(10\) mA
2. \(15\) mA
3. \(20\) mA
4. \(5\) mA

Which one of the following statement is false?

(1) Pure Si doped with trivalent impurities gives a p-type semiconductor 

(2) Majority carries in a n-type semiconductor are holes

(3) Minority carries in a p-type semiconductor are electrons

(4) The resistance of intrinsic semiconductor decreases with increase of temperature 

The device that can act as a complete electronic circuit is

1. Junction diode

2. Integrated circuit

3. Junction transistor

4. Zener diode

The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage waveforms of A, B and Y are as given

The logic gate is 

(1) $\mathrm{NOR}$ gate                                                 

(2) $\mathrm{OR}$ gate

(3) $\mathrm{AND}$ gate                                                 

(4) $\mathrm{NAND}$gate

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)