JEE Mains Previous Years Questions with Solutions

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1

AIEEE 2006

MCQ (Single Correct Answer)
An electric bulb is rated $220$ volt - $100$ watt. The power consumed by it when operated on $110$ volt will be
A
$75$ watt
B
$40$ watt
C
$25$ Watt
D
$50$ Watt

Explanation

The resistance of the bulb is $R = {{{V^2}} \over P} = {{{{\left( {220} \right)}^2}} \over {100}}$

The power consumed when operated at $110$ $V$ is

$P = {{{{\left( {110} \right)}^2}} \over {{{\left( {220} \right)}^2}/100}} = {{100} \over 4} = 25\,W$
2

AIEEE 2006

MCQ (Single Correct Answer)
A thermocouple is made from two metals, Antimony and Bismuth. If one junction of the couple is kept hot and the other is kept cold, then, an electric current will
A
flow from Antimony to Bismuth at the hot junction
B
flow from Bismuth to Antimony at the cold junction
C
now flow through the thermocouple
D
flow from Antimony to Bismuth at the cold junction

Explanation

At cold junction, current flows from Antimony to Bismuth (because current flows from metal occurring later in the series to metal occurring earlier in the thermoelectric series).
3

AIEEE 2005

MCQ (Single Correct Answer)
An energy source will supply a constant current into the load if its internal resistance is
A
very large as compared to the load resistance
B
equal to the resistance of the load
C
non-zero but less than the resistance of the load
D
zero

Explanation

$I = {E \over {R + r}},\,$ Internal resistance $\left( r \right)$ is

zero, $I = {E \over R} =$ constant.
4

AIEEE 2005

MCQ (Single Correct Answer)
The resistance of hot tungsten filament is about $10$ times the cold resistance. What will be resistance of $100$ $W$ and $200$ $V$ lamp when not in use ?
A
$20\Omega$
B
$40\Omega$
C
$200\Omega$
D
$400\Omega$

Explanation

$P = Vi = {{{V_2}} \over R}$

${R_{hot}} = {{{V^2}} \over P} = {{200 \times 200} \over {100}} = 400\Omega$

${R_{cold}} = {{400} \over {10}} = 40\Omega$

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