JEE Mains Previous Years Questions with Solutions

4.5
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1

AIEEE 2006

If the ratio of the concentration of electrons to that of holes in a semiconductor is ${7 \over 5}$ and the ratio of currents is ${7 \over 4},$ then what is the ratio of their drift velocities?
A
${5 \over 8}$
B
${4 \over 5}$
C
${5 \over 4}$
D
${4 \over 7}$

Explanation

${{{I_e}} \over {{I_h}}} = {{n{}_eeA{v_e}} \over {n{}_heA{v_h}}}$

$\Rightarrow {7 \over 4} = {7 \over 5} \times {{{v_e}} \over {{v_h}}}$

$\Rightarrow {{{v_e}} \over {{v_h}}} = {5 \over 4}$
2

AIEEE 2006

In a common base mode of a transistor, the collector current is $5.488$ $mA$ for an emitter current of $5.60mA.$ The value of the base current amplification factor $\left( \beta \right)$ will be
A
$49$
B
$50$
C
$51$
D
$48$

Explanation

${I_C} = 5.488\,mA,\,\,{I_e} = 5.6\,mA,\,{I_B} = {I_E} - {I_C}$

$\beta = {{{I_c}} \over {{I_B}}} = {{5.488} \over {5.6 - 5.485}} = 49$
3

AIEEE 2005

In a common base amplifier, the phase difference between the input signal voltage and output voltage is
A
$\pi$
B
${\pi \over 4}$
C
${\pi \over 2}$
D
$0$

Explanation

Zero; In common base amplifier circuit, input and output voltage are in the same phase.
4

AIEEE 2005

In a full wave rectifier circuit operating from $50$ $Hz$ mains frequency, the fundamental frequency in the ripple would be
A
$25$ $Hz$
B
$50$ $Hz$
C
$70.7$ $Hz$
D
$100$ $Hz$

Explanation

Input frequency, $f = 50\,Hz \Rightarrow T = {1 \over {50}}$

For full wave rectifier, ${T_1} = {T \over 2} = {1 \over {100}} \Rightarrow {f_1} = 100\,Hz.$