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Physics Electrons, waves and photos

Voltage, energy and power
Page 129
Chapter 11

The meaning of voltage

The voltmeter around a power supply will always read the same. This is because the voltmeter
measures the potential difference between two points. The two points will have the start voltage
e.g. 12,…

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Physics Electrons, waves and photos

Voltage and energy

Using the example above:
A 12 V power supply give 12 J of electrical energy to each coulomb of charge that passes
through it. Each coulomb of charge dissipates 8 J of energy as heat in the first resistor and 4 J…

Page 3

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Physics Electrons, waves and photos

Electrical power
The rate at which energy is transferred is known as power. Power is measured in watts. It is
defined as:

Power = Energy transferred / Time taken

P = W / t

Where P is the power and W is the energy transferred…

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Physics Electrons, waves and photos


A fuse is a device which is fitted in an electric circuit it is usually there to protect the wiring
from excessive currents. If there is an excessive current in the circuit the fuse will blow. This
happens for safety because high currents can…

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Physics Electrons, waves and photos

Power can be calculated by two equations:

Power = Current 2 x Resistance
P = I 2R

Power = Voltage 2 / Resistance
P = V 2 / R

These two equations can be used to calculate power waster as heat!

Calculating energy

Power =…

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Physics Electrons, waves and photos


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