NEET Physics Question - Current Electricity - Power of Electrical Circuit

Assertion (A): In the given circuit, \(r\) is variable, value of \(I\) is maximum when \(r = R\).

Reason (R): At \(r = R\) power produced across \(R\) is minimum.

(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)

(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(3) (A) is true but (R) is false

(4) Both (A) and (R) are false

Solution:

The current in the circuit is \(I = E / (R + r)\). For \(I\) to be maximum, the denominator \((R + r)\) must be minimum. This occurs when \(r = 0\), not \(r = R\). So, Assertion (A) is false. The power produced across \(R\) is \(P_R = I^2 R = (E / (R + r))^2 R\). As \(r\) increases, \(R+r\) increases, so \(P_R\) decreases. Thus, \(P_R\) is minimum when \(r\) is maximum (approaching infinity), not at \(r = R\). So, Reason (R) is also false.

Rankers Physics

Variable Resistor Circuit

Solution:

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