# Physics- Energy and electricity

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• Created by: BethanyM
• Created on: 12-01-14 14:27
What is the equation for energy?
power x time
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What is the unit for energy?
Joules
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What is the unit for power?
Watts
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What is the equation for energy efficiency?
(Useful energy transferred / Total energy supplied) x100
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How much is a unit of electricity?
1 kW
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How do you work out the total cost?
power (kW) x time (h) x cost per unit
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What is electricity?
The flow or movement of electrons
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What is a current?
A flow of electrons, measured by an ammeter
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If a magnet move into a coil of wire, will a positive or negative current be induced?
Positive
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Which three factors affect the size of the current in a generator most?
The strength of the magnet, the speed of the magnet and the number of coils.
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How does a simple generator work?
Coils rotate round two magnets. Attached to the end of the coils are slip rings, which rotate with the iron core. Carbon brushes brush against the slip rings, which creates electricity.
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Is an alternating or direct current produced in a simple generator?
Alternating current
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How does a dynamo work?
A rod with a magnet attached spins over a coil or wire. The rod spins with the wheel.
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Is an alternating or direct current produced in a dynamo?
Direct
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How do you calculate voltage?
Primary Voltage/Secondary Voltage = Turns on primary/Turns on secondary
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How is electricity transferred from power stations to homes?
Power station, step-up transformer, overhead power lines, step-down transformer, sub-station, home.
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What is the voltage of energy in UK homes?
230 kV
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Which renewable resources are available at all times?
Hydroelectricity, geothermal energy, wave power
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Which renewable resources are available at predicted times?
Solar energy, tidal energy
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Which renewable resources depend on the weather?
Solar energy, wind energy
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## Other cards in this set

### Card 2

#### Front

What is the unit for energy?

Joules

### Card 3

#### Front

What is the unit for power?

### Card 4

#### Front

What is the equation for energy efficiency?

### Card 5

#### Front

How much is a unit of electricity?