### JEE Mains Previous Years Questions with Solutions

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1

### AIEEE 2006

A solid which is not transparent to visible light and whose conductivity increases with temperature is formed by
A
Ionic bonding
B
Covalent bonding
C
Vander Waals bonding
D
Metallic bonding

## Explanation

Van der Waal's bonding is attributed to the attractive forces between molecules of a liquid. The conductivity of semiconductors (covalent bonding) and insulators (ionic bonding) increases with increase in temperature while that of metals (metallic bonding) decreases.
2

### 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

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

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

$\Rightarrow {{{v_e}} \over {{v_h}}} = {5 \over 4}$
3

### 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

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

$\beta = {{{I_c}} \over {{I_B}}} = {{5.488} \over {5.6 - 5.485}} = 49$
4

### 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.