The meter constant of a single-phase 240 V induction watthour

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The meter constant of a single-phase 240 V induction watthour meter is 400 r evolutions per kWh. The speed of the meter disc for a current of 10 amperes of 0.8 p.f. lagging will be ____________ rpm

1. 12.8 rpm
2. 1.8 rpm
3. 12 rpm
4. 11.8 rpm

Correct Option: A

n = k × power × time in hour

=	400 × 240 × 10 × 0.8	×	1	rph
	100		3600

= 12.8 rpm