1

### AIPMT 2000

The correct relation for $\alpha$, $\beta$ for a transistor
A
$\beta = {{1 - \alpha } \over \alpha }$
B
$\beta = {\alpha \over {1 - \alpha }}$
C
$\alpha = {{\beta - 1} \over \beta }$
D
$\alpha \beta = 1$

## Explanation

$\beta$ = ${{{I_C}} \over {{I_B}}}$ = ${{{I_C}} \over {{I_E} - {I_C}}}$ = ${{{{{I_C}} \over {{I_E}}}} \over {1 - {{{I_C}} \over {{I_E}}}}}$ = ${\alpha \over {1 - \alpha }}$
2

### AIPMT 2000

From the following diode circuit, which diode is in forward biased condition
A
B
C
D

## Explanation

A diode is said to be forward biased if p-type semiconductor of p-n junction is at positive potential with respect to n-type semiconductor of p-n junction. It is so for circuit (a).
3

### AIPMT 2000

The cations and anions are arranged in alternate form in
A
metallic crystal
B
ionic crystal
C
covalent crystal
D
semi-conductor crystal.

## Explanation

In an Ionic crystal, the cations and anions are arranged in alternate form.