Q42 of 146 Page 164

The commercial unit of energy is:

A. Watt B. Watt-hour


C. Kilowatt-hour D. Kilowatt

SI unit of energy is Joule.

Commercial unit of energy is KWh


1 KWh = 1 kW * 1 h


= 1000 W * 3600 s


1 watt – second = 1 Joule


1 kWh = 3600000 J

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40

An electric motor raises a load of 0.2 kg, at a constant speed, through a vertical distance of 3.0 m in 2 s. If the acceleration power stations and thermal power stations, alternators produce electricity

A. 0.3 B. 1.2


C. 3.0 D. 6.0

 41

An object is falling freely from a height x. After it has fallen a height, it will possess :

A. Only potential energy


B. Only kinetic energy


C. Half potential and half kinetic energy


D. Less potential and more kinetic energy

 43

How much energy does a 100 W electric bulb transfer in 1 minute?

A. 100 J B. 600 J


C. 3600 J D. 6000 J

 44

The device which converts mechanical energy into energy which runs our microwave oven is:

A. Electric motor


B. Alternator


C. Turbine


D. Electric heater