AC Ammeter Scale and Heating Effect – Rankers Physics
Topic: Alternating Current
Subtopic: Average Current and RMS Current

AC Ammeter Scale and Heating Effect

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

Solution:

\( \text{ac} \) 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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