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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is a fuse?

A

A thin piece of water which overheats and melts if the current is too high, protecting the circuit.

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2
Q

What are circuit breakers?

A

They consist of an automated electromagnetic switch which breaks the circuit if the current rises over a certain value.

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3
Q

Which is better, a fuse or a circuit breaker? why?

A

A circuit breaker because it can be reset and used again, and is much faster.

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4
Q

What do earth wires do?

A

They create a safe route for the current to flow through in the case of a short circuit, preventing electric shocks.

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5
Q

Do earth wires have a high or low resistance?

A

Very low resistance, so a strong current surges through them which breaks the fuse and disconnects the appliance.

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6
Q

What is double insulation?

A

Appliances with this either have plastic casings or have been designed so that the earth wire can not touch the metal casing, preventing them from giving an electric shock.

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7
Q

What is power measured in?

A

Watts (W).

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8
Q

What is the equation for power?

A

P=IxV (power = current x voltage)

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9
Q

What is direct current?

A

Current that only flows in one direction.

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10
Q

What is alternating current?

A

Current that continuously changes direction.

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11
Q

Give an example of an alternating current:

A

Mains electricity.

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12
Q

Give an example of an direct current:

A

Current supplied by a battery or cell.

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13
Q

What is current?

A

The rate of flow of charge.

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14
Q

What is the equation for charge?

A

Charge = current x time

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15
Q

What is the equation for voltage?

A

Voltage = current x resistance

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16
Q

What is the equation for energy transferred?

A

Energy transferred = current x voltage x time

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17
Q

What is the equation for final velocity?

A

v squared = u squared + 2as

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18
Q

What is the equation for force?

A

Force = change in momentum/time

19
Q

What is Q measured in?

A

Coulombs (C)

20
Q

What is current due to in metals?

A

Flow of electrons.

21
Q

What is potential difference measured in?

A

Volts.

22
Q

What is potential difference?

A

The work done per unit charge in moving between 2 points in a circuit.

23
Q

Where is a voltmeter placed?

A

In parallel with the component.

24
Q

What is resistance measured in?

A

Ohms.

25
Q

The greater the resistance, the…

A

The harder it is for current to flow through the component.

26
Q

What happens in an ohmic conductor?

A

The current is directly proportional to the voltage (it has constant resistance).

27
Q

What happens in an non-ohmic conductor?

A

The resistance changes as current and voltage changes.

28
Q

Why is there increased resistance in a filament lamp?

A

Because the current increases through the filament, so does the temperature, which means electrons and ions vibrate more, increasing resistance.

29
Q

What is a thermistor?

A

It’s a resistor who’s resistance decreases as temperature increases

30
Q

What is a light dependent resistor?

A

A resistor who’s resistance decreases as light intensity increases.

31
Q

What happens to current in series circuits?

A

The same current flows through every component.

32
Q

What happens to potential difference in series circuits?

A

It’s shared across each component.

33
Q

What happens to current in parallel circuits?

A

The current is shared between each branch

34
Q

What happens to potential difference in parallel circuits?

A

It’s the same across every branch.

35
Q

What are 3 advantages of parallel circuits?

A

-Components (e.g. bulbs) may be switched on/off independently.
-If one component breaks, current can still flow through the other parts of the circuit.
-Bulbs maintain a similar brightness.

36
Q

What are 2 advantages of series circuits?

A

-Fewer wires, cheaper and easier to assemble.
-Uses less power

37
Q

What happens to current as voltage increases?

A

As voltage increases, current increases too.

38
Q

What happens the more components in a circuit?

A

The more components in a circuit, the lower the current.

39
Q

Describe the qualitative effect of changing resistance on the current in a circuit:

A

Since V = I x R, as you increase the resistance in a circuit, the current will decrease.

40
Q

What is voltage?

A

The energy transferred per unit charge passed.

41
Q

What is a volt?

A

A joule per coulomb.

42
Q

Identify 3 common materials which are electrical conductors:

A

Metals such as copper, tin and gold.

43
Q

Identify 3 common materials which are electrical insulators:

A

Rubber, glass and wood.

Physics (4 decks)

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