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Physics > 4th - Current And Mains Electricity > Flashcards

4th - Current And Mains Electricity Flashcards

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1
Q

What is current measured in (amps

A

Coloumbs per second C/s

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2
Q

What is voltage measured in (volts)

A

Joule per coloumb J/C

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3
Q

What is power measured in (watt)

A

Joule per second J/s

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4
Q

How is a frayed cable a hazard

A

Plastic insulation no longer intact
May be short circuit
- risk of electric shock
- heating and risk of fire

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5
Q

How is long cable a hazard

A

Long cables have larger resistances
- wire will heat up and cause a fire

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6
Q

How are damaged plugs a hazard

A

Plastic insulation/ cover is missing/broken
- live wires are exposed
- risk of electric shock

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7
Q

How is water around socket a hazard

A

Water in electrical equipment, allows electricity to conduct to outside
- cause electric shock

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8
Q

How is pushing metal into sockets a hazard

A

Metal is a good conductor
- risk of electric shock

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9
Q

What is plug casing made of and why

A

Plastic - insulator
- current cant pass through
- no risk of electric shock

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10
Q

What is wire covering made of and why

A

Plastic - insulator
- current cant pass through ]
- no risk of electric shock
- wont short circuit

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11
Q

What are progs made of and why

A

Brass - conductor
- current easily passes through
- no malleable so prongs wont bend

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12
Q

What are wires made of and why

A

Copper - good conductor

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13
Q

What colour is the live wire

A

Brown

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14
Q

What colour is the neutral wire

A

Blue

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15
Q

What colour is the earth wire

A

Green and yellow

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16
Q

What is the purpose of the earth wire

A

To keep user safe form electric shock

17
Q

Voltage of live wire

A

Alternates between +230v and -230V

18
Q

Voltage of neutral wire

A

0 v

19
Q

What is the earth wire connected to

A

The metal casing of the appliance

20
Q

What happens if the live wire touches the metal casing

A
  • The casing is earthed due to the earth wire
  • a big current flows through live wire -> case -> down earth wire
  • surge in current melts the fuse -> cuts off the live supply (breaks circuit)
21
Q

What does fuses prevent

A

The risk of fire

22
Q

How should fuses be rated

A

As near as possible to the current, but just a bit higher than the normal current

23
Q

What does it mean when an appliance is double insulated

A
  • made of plastic casing, or electrics are completely encased in a plastic cover
  • only needs a live and neutral wire
24
Q

What happens if u pass current through a resistor or wire

A

Both will heat up
Electrical energy is transferred to heat energy

25
Q

The metal ions in a fuse is vibrating in position. This means that free ….

A

Free electrons will collide with the metal ions
And transfer the energy to the lattice in the form of heat

26
Q

If you increase current enough, what is produced

A

Heat produced in the wire is enough to melt it
= the fuse has blown
= now safe

27
Q

Current, voltage, power

A

Power = current x voltage
Change 100 milli amps to 0.1 amps

28
Q

What is power

A

The rate of transfer of energy

29
Q

Current, voltage, energy transferred, time

A

Energy transferred = current x voltage x time
Time has to be seconds

30
Q

What is the difference between a DC and an AC current

A

DC - current only travels in one direction
AC - current constantly changes direction

31
Q

What current is a main supply (DC or AC)

A

AC
- high voltage of 230v
- doesnt need replacing
- not portable

32
Q

What current is a battery supply (DC or AC)

A

DC
- low voltage
- needs replacing / recharging
- portable

33
Q

What does charge need to flow

A

Potential difference and a complete circuit

34
Q

What is current

A

The rate of flow of charge

35
Q

What is high current

A

More charge (Q) flowing past a point in a circuit per second

36
Q

What is low current

A

Less charge (Q) flowing past a point in a circuit per second

37
Q

Charge, current, time

A

Current = charge / time

38
Q

What is the direction for current

A

From positive to negative (big line to small line)

39
Q

Why do bulbs light instantly

A

Electrons (charge) are found everywhere in a circuit, but the push from the cell makes them move

Physics (7 decks)

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