1

### 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.
2

### 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
3

### 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
4

### AIPMT 2001

The current in the circuit will be

A
5/40 A
B
5/50 A
C
5/10 A
D
5/20 A

## Explanation

D1 is reverse biased and D2 is forward biased.

$\therefore$ I = ${5 \over {30 + 20}}$ = ${5 \over {50}}$ A