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Physics > Physics P2 > Flashcards

Physics P2 Flashcards

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1
Q

What is current?

A

The flow of electrical charge

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2
Q

What is meant by potential difference?

A

Potential difference (or current) is the driving force that pushes the charge around

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3
Q

What is the unit for potential difference?

A

Volt, V

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4
Q

What is resistance?

A

Anything that slows the flow down

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5
Q

What is the unit for resistance?

A

ohms

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6
Q

Name a linear component

A

fixed resistor

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7
Q

Name a non-linear component

A

filament lamp
diode

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8
Q

Does the resistance of an LDR increase with light intensity?

A

No.
In bright light, resistance falls
In darkness, resistance increases

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9
Q

What happens to the resistance of a thermistor as it gets hotter?

A

It drops

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10
Q

Is potential difference shared between components in a series circuit?

A

yes

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11
Q

How does the current through each component vary in a series circuit?

A

The same current flows through all components.
The size of the current is determined by the total potential difference of the cells and the total resistance of the circuit.

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12
Q

What is an alternating current?

A

one that changes direction

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13
Q

What is the potential difference and frequency of the UK mains supply?

A

230V
50Hz

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14
Q

What are the three wires and the colours in a three-core cable?

A

LIVE WIRE - brown
NEUTRAL WIRE - blue
EARTH WIRE - green and yellow

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15
Q

Why are the wires in a three-core cable colour-coded?

A

To make it easy to tell them apart

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16
Q

Why is touching a live wire dangerous?

A

Can give you an electric shock.
Your body, like the Earth, is at 0V. If you touch a live wire, a large pd is produced across your body and a current flows through you.

17
Q

Are you still in danger if a plug socket or light switch is turned off?

A

Yes, because a current isn’t flowing BUT there is still pd in the live wire.

18
Q

Explain the energy transfers in an electrically-powered fan:

A

Energy is transferred electrically from the battery of a handheld fan to the kinetic energy store of the fan’s motor.

19
Q

What is the power rating of an appliance?

A

The energy it transfers per second

20
Q

What is the national grid?

A

A giant web of wires that covers the whole of Britain, getting electricity from power stations to homes everywhere.

21
Q

Why is electricity transferred by the national grid at a high potential difference but low current?

A

It is cheaper.
Increased pd = decreased current -> decreasing energy lost by heating the wires and the surroundings, making the national grid more efficient.

22
Q

What are the functions of step-up and step-down transformers?

A

Step-up = increased potential difference, decreasing the current.
Step-down = decreased potential difference, increasing the current

Physics (10 decks)

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