In electrodynamometer movement, the deflection of the pointer is:

Question

Question

This question was previously asked in

UPPCL JE Electrical 8 Sept 2021 Official Paper (Shift 2)

Answer 1

Name of Instrument	Deflection	Measured Value
Moving coil instrument	θ ∝ I	Average value
Moving iron instrument	θ ∝ I2	RMS value
Electrodynamometer instrument	θ ∝ I1I2 ∝ I2	RMS value
Hotwire instrument	θ ∝ I2	RMS value

In all instruments except the Moving coil, the measured value is directly proportional to the square of response. They exhibit square law.

Additional Information

Name of Instrument	PMMC	MI	Electrodynamometer
Deflecting Torque (Td)	BINA	\(\frac{1}{2}{I^2}\left( {\frac{{dL}}{{d\theta }}} \right) \)	\({I_1}{I_2}cos\phi \left( {\frac{{dM}}{{d\theta }}} \right) \)
Deflection (θ)	\(\frac{{BINA}}{{{K_C}}} \)	\(\frac{1}{2}\frac{{{I^2}}}{{{K_c}}}\left( {\frac{{dL}}{{d\theta }}} \right) \)	\({I_1}{I_2}cos\phi \frac{1}{{{K_c}}}\left( {\frac{{dM}}{{d\theta }}} \right)\)

Where B is flux density in Tesla.

N is the number of turns

A is a cross-section area.

I is the current flowing through the instrument.

L is self-inductance and M is mutual-inductance.