| Assertion (A): The balancing point of a meter bridge is obtained at L = 40 cm. When the area of cross-section of the wire of is doubled, the balancing point shifts to L = 60 cm. |
| Reason (R): Resistance of wire is directly proportional to its area of cross - section. |
A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is NOT the correct explanation of A
C) A is true but R is false
D) A is false and R is true
Correct Answer: D
Solution :
| Option [d] is correct. |
| Explanation: For a meter bridge, at the balancing point \[\frac{R}{X}=\frac{L}{100-L}\] which is independent of the area of cross section. So, the assertion is false. |
| Resistance of wire is inversely proportional to its area of cross-section since R = R=\[\rho \frac{L}{\operatorname{A}}\]. So reason is also false. |
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