1

### JEE Main 2016 (Online) 9th April Morning Slot

An unknown transistor needs to be identified as a npn or pnp type. A multimeter, with + ve and − ve terminals, is used to measure resistance between different terminals of transistor. If terminal 2 is the base of the transistor then which of the following is correct for a pnp transistor ?
A
+ ve termial 1, $-$ve terminal 2, resistance high
B
+ ve termial 2, $-$ve terminal 1, resistance high
C
+ ve termial 3, $-$ve terminal 2, resistance high
D
+ ve termial 2, $-$ve terminal 3, resistance low

## Explanation + ve terminal at 1, $-$ ve terminal at 2 and resistance high for pnp transistor.
2

### JEE Main 2016 (Online) 9th April Morning Slot

An experiment is performed to determine the I - V characteristics of a Zener diode, which has a protective resistance of R = 100 $\Omega$, and a maximum power of dissipation rating of 1 W. The minimum voltage range of the DC source in the circuit is :
A
0 $-$ 5 V
B
0 $-$ 8 V
C
0 $-$ 12 V
D
0 $-$ 24 V

## Explanation Potential drop accross zener diode.

Vz = V $-$ 100 I

$\therefore$   Power dissiption = Vz I

= (V $-$ 100 I) I

Given that,

(V $-$ 100 I) I = 1

$\Rightarrow$   VI $-$ 100 I2 = 1

$\Rightarrow$   100 I2 $-$ VI + 1 = 0

As   As I is real,

So, b2 $-$ 4ac $\ge$ far this quadratic equation.

$\therefore$   V2 $-$ 4(100)1  $\ge$ 0

$\Rightarrow$   V $\ge$ 20 V

$\therefore$   Voltage range should be 0 $-$ 24 V
3

### JEE Main 2016 (Online) 10th April Morning Slot

The ratio (R) of output resistance r0, and the input resistance ri in measurements of input and output characteristics of a transistor is typically in the range:
A
R ~ 102 $-$ 103
B
R ~ 1 $-$ 10
C
R ~ 0.1 $-$ 0.01
D
R ~ 0.1 $-$ 1.0

## Explanation

R $=$ ${{{r_0}} \over {{r_i}}} \equiv 1 - 10$
4

### JEE Main 2016 (Online) 10th April Morning Slot

A realistic graph depicting the variation of the reciprocal of input resistance in an input characteristics measurement in a commonemitter transistor configuration is :
A B C D ## Explanation For common emitter configuration, the input characteristic graph is shown above,

ri $=$ ${{\Delta {V_{BE}}} \over {\Delta {{\rm I}_B}}}$

$\Rightarrow$   ${1 \over {{r_i}}} = {{d{{\rm I}_B}} \over {d{V_{BE}}}}$ $=$ shope of this curve.

Upto knee voltage 0.7 V the shope is almost constant. Then it increases sharply.

So, option (c) is the correct choice.