Assertion (A) : Longer wires have greater resistance and the smaller wires have lesser resistance.

Reason (R) : Resistance of a wire increases with increase in temperature.

1. both A and R are true and R is the correct explanation of A
2. both A and R are true and R is not the correct explanation of A
3. assertion is false but reason is true
4. assertion is true but reason is false

both A and R are true and R is not the correct explanation of A

Explanation

Assertion (A) is true because the number of collisions suffered by the moving electrons will be more if they have to travel a longer distance in a wire, therefore, a long wire offers more resistance than a short wire (i.e., resistance of a wire ∝ length of wire).

Reason (R) is true because if the temperature of wire increases, electrons in it vibrate more violently. As a result, the number of collisions increases and hence the resistance of wire increases (i.e., the resistance of a wire increases with the increase in its temperature).

The assertion talks about wire length, but the reason explains the effect of temperature. So, although both statements are true, the reason does not explain the assertion.