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Current Electricity question

2008 · Shift 0 · Q71

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2008 · Shift 0 · Q71

Current Electricity question

2008 · Shift 0 · Q71

JEE MainPhysicsCurrent ElectricityMCQ+4 / −1

Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. AIEEE 2008 Physics - Current Electricity Question 311 English

AIEEE 2008 Physics - Current Electricity Question 311 English

The value of the unknown resister

R

is

A
$13.75\Omega$
B
$220\Omega$
C
$110\Omega$
D
$55\Omega$

View written solutionFree

Correct answer: B

Principle of meter bridge

For a meter bridge at null deflection,

$\frac{R}{S} = \frac{l}{100-l}$

where:

$R$ = unknown resistance,
$S$ = known resistance,
$l$ = balancing length from one end.

Reading the figure

From the given setup, the known resistance in the other gap is $220\,\Omega$ , and the balance point is at the midpoint of the wire, i.e.

$l = 50\,\text{cm}$

Apply balance condition

$\frac{R}{220} = \frac{50}{100-50} = \frac{50}{50} = 1$

Thus,

$R = 220\,\Omega$

Check options

A: $13.75\,\Omega$ ✗
B: $220\,\Omega$ ✓
C: $110\,\Omega$ ✗
D: $55\,\Omega$ ✗

Hence, the correct answer is Option B.

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