1

### AIPMT 2002

The given truth table is for which logic gate

$\matrix{ A & B & Y \cr 1 & 1 & 0 \cr 0 & 1 & 1 \cr 1 & 0 & 1 \cr 0 & 0 & 1 \cr }$
A
NAND
B
XOR
C
NOR
D
OR.

## Explanation

This truth table represents NAND gate. 2

### AIPMT 2002

In a p-n junction
A
high potential at n side and low potential at p side
B
high potential at P side and low potential at n side
C
p and n both are at same potential
D
undetermined.

## Explanation

For conduction, p-n junction must be forward biased. For this p-side should be connected to higher potential and n-side to lower potential.
3

### AIPMT 2002

For a transistor ${{{I_C}} \over {{I_E}}}$ = 0.96, then current gain for common emitter is
A
12
B
6
C
48
D
24

## Explanation

${{{I_C}} \over {{I_E}}}$ = 0.96 = $\alpha$

$\therefore$ Current gain, $\beta$ = ${{{I_C}} \over {{I_B}}}$ = ${\alpha \over {1 - \alpha }}$ = 24
4

### AIPMT 2002

Number of atom per unit cell in B.C.C.
A
9
B
4
C
2
D
1

## Explanation

In body-centred cubic (b.c.c.) lattice there are eight atoms at the corners of the cube and one at the centre.

Therefore number of atom per unit cell

= ${1 \over 8} \times 8$ + 1 = 2