Ammeter Resistance and Shunt – Rankers Physics
Topic: Current Electricity
Subtopic: Measuring Devices ( Galvanometer, Voltmeter and Ammeter & Meter Bridge )

Ammeter Resistance and Shunt

Assertion (A): Resistance of ammeter is less than resistance of milliammeter, (If made from same galvanometer).
Reason (R): Value of shunt resistance in case of ammeter is more than a milliammeter.
 
(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:

An ammeter is designed to measure larger currents than a milliammeter. To achieve a larger current range with the same galvanometer, a smaller shunt resistance is required to bypass a greater portion of the total current. A smaller shunt resistance results in a lower overall resistance for the ammeter. Thus, Assertion (A) is true. Reason (R) states the shunt resistance for an ammeter is more than a milliammeter, which is false; it must be less.

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