# One single phase wattmeter operating on 230V and 5A for 5 hours makes 1940 revolutions. Meter constant in revolutions is 400. What is the power factor of the land?

A. 1

B. 0.84

C. 0.73

D. 0.65

**Answer: Option B **

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kWh consumed=230 x 5 x 5 =5.750 kWh

meter constant= 400 rev/kWh

rev for 5 hours = 1940

kWh= rev/ meter constant= rev/rev/kWh =1940/400=4.85 kWh

Actual power factor=4.85/5.75=0.843

Energy consumed = 230 × 5 × 5 = 5750 Wh

= 5.57 kWh Revolution constant = 400 rev/kWh

∴ kWh =

1940

= 4.8

400

Power factor =

4.8

= 0.8

Aparrent power (kvah)= 230×5x5/1000=5.750

Active power (KWh)= 1940/400=4.85

P.f (Cos €) =KWh/Kvah= 4.85/5.75=0.843

kWh consumed=230 x 5 x 5 =5.750 kWh

meter constant= 400 rev/kWh

rev for 5 hours = 1940

kWh= rev/ meter constant= rev/rev/kWh =1940/400=4.85 kWh

Actual power factor=4.85/5.75=0.843

GIVEN V=230V, I=5A& T=5 Hours

meter constant =400, revolution=1940

energy (E)=REVOLUTION/ METER CONSTANT

energy (E)=1940/400 =4.85 KWH = 4850WH

Energy consumed(E) = 230v *5A * 5 hours = 5.750 kwh = 5750 WH

POWER FACTOR = 4850/5750 =0.843

Energy consumed = 230v *5A * 5 hours = 5.750 kwh

Revolution constant =400/kwh so =1940/400= 4.85

P.F = 4.85/5.750= 0.84

@hari

please explain this question sir.