AC Ammeter Scale and Heating Effect – Rankers Physics

Average Current and RMS Current: Practice Problem & Solution

Assertion (A): The divisions are equally marked on the scale of \( \text{ac} \) ammeter. Reason (R): Heat produced is directly proportional to the current.  
(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

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Average Current and RMS Current. Understanding the underlying formula is key to arriving at the correct answer below:

\( \text{ac} \) ammeters (hot wire type) measure current based on the heating effect, where heat produced is \( H \propto I^2 \). This quadratic relationship results in a non-linear scale, not equally marked. Thus (A) is false. Heat produced is proportional to the square of the current, not directly, so (R) is also false.

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