Q60 / 69 · JEE Advanced 2008 (Paper 1) · Physics
Statement $1 \mathrm{In}$ a Meter Bridge experiment, null point for an unknown resistance is measured. Now, the unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same point as before by decreasing the value of the standard resistance.
and Statement 2 Resistance of a metal increase with increase in temperature.
- AStatement 1 is true, Statement 2 is true, Statement 2 is a correct explanation for Statement 1.
- BStatement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation for Statement 1.
- CStatement 1 is true, Statement 2 is false.
- Correct answerDStatement 1 is false, Statement 2 is true
Solution
With increase in temperature, the value of unknown resistance will increase.
In balanced Wheatstone bridge condition, $\frac{R}{X}=\frac{l_1}{l_2}$
Here, $R=$ value of standard resistance,
$X=$ value of unknown resistance .
To take null point at same point or $\frac{l_1}{l_2}$ to remain unchanged, $\frac{R}{X}$ should also remain unchanged. Therefore, if $X$ is increasing $R$ should also increase.
$\therefore$ correct option is (d).
Hence, the correct answer is option: 'D'.