Physics P2 5.4 Electrical power and potential difference.

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What is the power supplied to a device?
The energy transferred to it each second.
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What is the correct rating for a fuse?
Correct rating (in amperes) for a fuse = electrical power (watts) over potential difference (volts).
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What does an electrical appliance do?
Transfers electrical energy into other forms of energy.
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What is the rate at which an electrical appliance transfers electrical energy into other forms of energy called?
Power.
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What is the equation used to calculate power?
P = E over t.
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In the equation to calculate power, what is P?
The power in watts (W).
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In the equation to calculate power, what is E?
The energy transferred in joules (J).
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In the equation to calculate power, what is t?
The time in seconds (s).
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In an electrical circuit, what is it more usual to measure?
The current through an appliance and the potential difference across it rather than the energy transferred and the time.
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What equation can be used to calculate the power of an appliance using current and pd?
P = (looks like a slanted I but look up) over V.
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In the equation to calculate power using current and pd, what is P?
The power in watts (W).
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In the equation to calculate power using current and pd, what is the thing that looks like a slanted I?
The current in amperes (A).
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In the equation to calculate power using current and pd, what is V?
The potential difference in volts (V).
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How can you tell the power rating of an electrical appliance?
It is shown on the appliance.
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What is the pd of the mains supply?
230 V.
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What can the equation to calculate power using current and pd be used for?
To calculate the normal current through an appliance and so work out the size of fuse to use.
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How is a fuse chosen?
So that its value is slightly higher than the calculated current.
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What is the current in a steam wallpaper stripper that has a power of 2kW?
P = slanted I over V, then slanted I equals P over V, then slanted I = 2000 W / 230 V, then slanted I = 8.7 A.
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What is the power , in kW, of an appliance that transfers 90 000 J of energy in 30 seconds?
3 kW.
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What is the power of a mains appliance that takes a current of 10 A?
2300 kW.
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**PRACTICE CALCULATING THE CURRENT IN APPLIANCES OF DIFFERENT POWERS SO YOU CAN CHOOSE THE CORRECT FUSE**
**LOOK UP CHANGING A FUSE**
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Card 2

Front

What is the correct rating for a fuse?

Back

Correct rating (in amperes) for a fuse = electrical power (watts) over potential difference (volts).

Card 3

Front

What does an electrical appliance do?

Back

Preview of the front of card 3

Card 4

Front

What is the rate at which an electrical appliance transfers electrical energy into other forms of energy called?

Back

Preview of the front of card 4

Card 5

Front

What is the equation used to calculate power?

Back

Preview of the front of card 5
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