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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is the unit for current?

A

Amperes, A

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2
Q

What is the unit for voltage?

A

Volts, V

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3
Q

What IS current?

A

the rate of flow of charge

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4
Q

What is the unit for energy?

A

Joules, J

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5
Q

What is the unit for resistance?

A

Ohms, Ω

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6
Q

What IS voltage?

A

energy transferred per unit charge, joules per coulomb

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7
Q

What is the unit for power?

A

Watts, W

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8
Q

What is the equation for charge?

A

charge = current x time (Q=IT)

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9
Q

What is the equation for resistance, voltage and current?

A

voltage = current x resistance (V=IR)

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10
Q

What is the equation for power?

A

power = current x voltage (P=IV)

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11
Q

What is the equation for energy transferred?

A

energy transferred = power (IV) x time (E=PT)

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12
Q

Mains electricity has an…current

A

alternating current

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13
Q

Batteries have a…current

A

direct current

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14
Q

What happens to the current when you increase the resistance?

A

less current can flow

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15
Q

What colour is the neutral wire?

A

blue

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16
Q

What colour is the live wire?

A

brown

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17
Q

What colour is the earth wire?

A

green and yellow

18
Q

What are the safety features of a plug (the plug itself)?

A
  • right coloured wire connected to each pin - no bare wires showing inside plug - cable grip tightly fastened over the cable outer layer - metal parts made of copper or brass (good conductors) - case, cable grip and cable insulation made of rubber or plastic (good insulators and flexible)
19
Q

Order of wires in a plug?

A

neutral, earth, live

20
Q

What does the neutral wire do?

A

current flows out of the neutral wire, which always has 0V

21
Q

What does the live wire do?

A

current flows in via the live wire, which alternates between a high negative and positive (alternating) voltage of 230V

22
Q

What does the earth wire do?

A

when there is a fault and the live touches the case, a large current builds up in the live, through the case and is sent down the earth wire.

23
Q

Safety precautions when using plugs?

A
  • damaged (missing/ cracked/ broken case) so that there aren’t exposed live wires which could give you a shock - cable isn’t frayed, exposed live wires - cables aren’t too long, trip hazard - no water near electrics, good conductor - no metal objects in plug as good conductor
24
Q

A plug with metal casing…

A

must be earthed to an earth wire so that the conductor can never become live

25
Q

A plug with plastic casing…

A

is double insulated. Plastic is an insulator so stops current flowing. Doesn’t need an earth wire.

26
Q

What does a fuse do?

A

when a fault develops, a surge of current flows though the live and then the earth. This melts the fuse which cuts off the live supply. This isolates the appliance which means you can’t get shocked and reduces the fire risk

27
Q

What does a circuit breaker do?

A

when a circuit breaker detects a surge in current it breaks the circuit by opening a switch

28
Q

What are the advantages of a circuit breaker over a fuse?

A
  • works faster - doesn’t have to be replaced, can be reset - works for small current charges which might not melt a fuse but are still dangerous
29
Q

What is an RCCB?

A

residual current circuit breaker, detects a difference in current between the neutral and the live wire and cuts the circuit

30
Q

What happens when electric current passes through a resistor?

A

there is a heating effect on the resistor which increases the resistor’s resistance, meaning less current can flow.

31
Q

What are the advantages of the heating effect due to a current in a resistor?

A
  • melts fuses - can be used in toasters to cook bread
32
Q

What IS power?

A

the rate of energy transfer

33
Q

What do you need to know to work out a fuse rating?

A

current

34
Q

An ammeter must be placed in…

A

series

35
Q

A voltmeter must be placed in…

A

parallel

36
Q

the gradient of an I-V graph is…

A

1/Resistance

37
Q

Metal filament lamp I-V graph

A

as temperature increases, resistance increases, hence curve.

38
Q

Wire I-V graph

A

current at a contant temp is proportional to voltage

39
Q

Diode I-V graph

A

current will only flow in one direction

40
Q

Different resistors I-V graph

A

current through a resistor at a constant temp is proportional to voltage. Different resistors have different resistances, hence slope.

Physics (7 decks)

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