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Physics⚡️ > Chapter 5 🗽 > Flashcards

Chapter 5 🗽 Flashcards

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1
Q

What is the equation for energy transferred from the mains?

A

Energy transferred from the mains (J)= power x time

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2
Q

What is the equation for power supplied (W)?

A

Power = current x potential difference

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3
Q

How do electrical appliances waste energy?

A

Heating the surroundings

Friction in moving parts

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4
Q

Equation for efficiency

A

Efficiency = output power/input power x 100

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5
Q

What is charge flow?

A

The electrons being forced round a circuit

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6
Q

Equation for charge flow

A

Charge flow (C) = current x time

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7
Q

When the charge flows around a circuit for a given time, the envy supplied by the battery is equal to what?

A

The energy transferred to all the components in a circuit

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8
Q

Why does a resistor get hot when charge flows through it?

A

Energy is transferred to the resistor because the electrons collide with the resistor ions, heating it up

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9
Q

What is the equation for power?

A

Power = energy transferred/time

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10
Q

What is the current in an electrical appliance?

A

The current is the charge that flows through it each second

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11
Q

What is the potential difference of an electrical appliance?

A

The energy that is transferred to the appliance by the charge passing through it

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12
Q

Equation for power supplied?

A

Power supplied = current x potential difference

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13
Q

Equation for power using current and resistance

A

Power = current^2 x resistance

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14
Q

What does the earth wire do?

A

It carries the current into the earth if something goes wrong

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15
Q

Why are plugs, sockets and cables made of insulators?

A

To stop them carrying a current

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16
Q

What is the potential difference of the earth wire?

A

0V

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17
Q

Why are the pins made of brass?

A

Brass is a good conductor and doesn’t rust

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18
Q

What does the fuse do?

A

If the current gets too high, it melts and cuts the live wire off

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19
Q

Which is the brown wire?

A

The live wire

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20
Q

Which is the blue wire?

A

The neutral wire

21
Q

Which is the yellow and green wire?

A

Earth wire

22
Q

Why is plastic used?

A

It is a good insulator so you don’t get an electric shock

23
Q

What are two core cables used for?

A

Appliances with plastic cases

24
Q

Why must some wires be thicker than others?

A

Carry different currents

25
Q

What happens when a plug short circuits?

A

The live wire touches the neutral wire

26
Q

Why is copper used in the wires?

A

It is a good conductor and bends easily

27
Q

What is a direct current?

A

When the current flows in only one direction

28
Q

What is an alternating current?

A

When the current repeatedly reverses direction

29
Q

What is frequency in the uk mains?

A

50Hz

30
Q

What is a step up transformer?

A

Used to make the size of the potential difference much bigger

31
Q

What is a step down transformer?

A

Used to supply homes with electricity from the national grid

Takes voltage down to manageable level

32
Q

How do you measure the frequency of an ac supply?

A

Frequency = 1/ time taken for one cycle

33
Q

what does the live wire do?

A

carries current to the appliance

34
Q

what does the neutral wire do?

A

carries current away from the appliance

35
Q

1 kw

A

1000 w

36
Q

What are the two ways in which efficiency can be expressed

A

Ratio or percentage

37
Q

Why do electric appliances ways energy because of the wires

A

The wires have some resistance so the energy is transferred as heat

38
Q

What does a domestic electricity meter measure

A

How much energy is supplied with

39
Q

What is the energy supplied by the battery equal to

A

The energy transferred to all components in the circuit

40
Q

How to determine what fuse to use

A

Use the equation current = power / PD

You use the fuse closest to it

41
Q

What determines whether an appliance should have a 3 or 2 core cable

A

2 core cables are for appliances with plastic cases

42
Q

Why are some wires thicker than others

A

Carry more charge

43
Q

What causes a short circuit

A

When the live wire touches the neutral wire

44
Q

Difference between 2 and 3 core wire

A

2 core doesn’t have an earth wire

45
Q

What is the PD of electricity in the UK

A

325 v

46
Q

Why is the PD of the national grid so high?

A

Much less current is needed to transfer same amount of power

47
Q

What is the live wire in a mains circuit charge like

A

Alternately positive and negative

48
Q

Which wire is earthed at the local power station?

A

Neutral

49
Q

What does double insulated mean?

A

The wires are coated in plastic and the outer case of the appliance is plastic

Physics⚡️ (16 decks)

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