Electrical power
Power P in an electrical circuit is given by the product of potential difference V and current I, as stated in Chapter 1. The unit of power is the watt,W.
From Ohm’s law, V =IR. Substituting for V in equation (1) gives:
Also, from Ohm’s law, I =V/R. Substituting for I in equation (1) gives:
There are thus three possible formulae which may be used for calculating power.
Electrical energy
then the unit of energy is kilowatt-hours, often called the ‘unit of electricity’. The ‘electricity meter’ in the home records the number of kilowatt-hours used and is
thus an energy meter.
Power P in an electrical circuit is given by the product of potential difference V and current I, as stated in Chapter 1. The unit of power is the watt,W.
From Ohm’s law, V =IR. Substituting for V in equation (1) gives:
Also, from Ohm’s law, I =V/R. Substituting for I in equation (1) gives:
There are thus three possible formulae which may be used for calculating power.
Electrical energy
Electrical energy = power × time
If the power is measured inwatts and the time in seconds then the unit of energy is watt-seconds or joules. If the power is measured in kilowatts and the time in hoursthen the unit of energy is kilowatt-hours, often called the ‘unit of electricity’. The ‘electricity meter’ in the home records the number of kilowatt-hours used and is
thus an energy meter.
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