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# Electric energy and electric power

If I is the current flowing through a conductor of resistance R in time t, then the quantity of charge flowing is, q = It.

Electric energy and electric power.

If I is the current flowing through a conductor of resistance R in time t, then the quantity of charge flowing is, q = It. If the charge q, flows between two points having a potential difference V, then the work done in moving the charge is = Vq = V It.

Then, electric power is defined as the rate of doing electric work. Electric power is the product of potential difference and current strength.

Since V = IR, Power = I2R

Electric energy is defined as the capacity to do work. Its unit is joule. In practice, the electrical energy is measured by watt hour (Wh) or kilowatt hour (kWh). 1 kWh is known as one unit of electric energy.

(1 kWh = 1000 Wh = 1000 �- 3600 J = 36 �- 105 J)

Wattmeter

A wattmeter is an instrument used to measure electrical power consumed i.e energy absorbed in unit time by a circuit. The wattmeter consists of a movable coil arranged between a pair of fixed coils in the form of a solenoid. A pointer is attached to the movable coil. The free end of the pointer moves over a circular scale. When current flows through the coils, the deflection of the pointer is directly proportional to the power.

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