Moving Coil Ammeter/Voltmeter – Rankers Physics

Average Current and RMS Current: Practice Problem & Solution

Assertion (A): The moving coil ammeters or voltmeters can't be employed to measure alternating current or voltage respectively. Reason (R): If an alternating current is passed through a moving coil ammeter or voltmeter, then the average value of torque experienced by the coil is zero.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
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:

Moving coil instruments measure the average value of current. For AC, the average value over a full cycle is zero, resulting in zero average torque. Hence, moving coil ammeters/voltmeters cannot measure AC. Both assertion and reason are true, and the reason correctly explains the assertion.

Leave a Reply

Your email address will not be published. Required fields are marked *

Similar Practice Questions

Explore conceptually related problems to test your knowledge.

1. In an LCR series circuit the potential differences across the resistance, capacitance and inductance are \(80\text{ V}\), \(40\text{ V}\) and \(100\text{ V}\) respectively. The power factor of this circuit is:
2. Two cables of copper are of equal lengths. One of them has a single wire of area of cross-section A, while other has 10 wires of cross-sectional area A/10 each. Give their suitability for transporting A.C. and D.C (1994)
3. In an a.c. circuit with phase voltage V and current I, the power dissipated is (1997)
4. Assertion (A): At resonance in AC circuits current and emf are in phase. Reason (R): At resonance in AC circuits, current is maximum.  
5. Consider a series \(LCR\) circuit in which reactance and resistance are \(100\ \Omega\) each. When the circuit is connected to ac source \(220\text{ V}\), \(50\text{ Hz}\), then current drawn from the source is