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GCSE Physics > P5 - Electricity In The Home✔️ > Flashcards

P5 - Electricity In The Home✔️ Flashcards

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1
Q

What is direct current (d.c.)?

A

Current which goes arround the circuit in only one direction, example: is batterys used to power a torch

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2
Q

What is alternating current (a.c.)?

A

Alternating current repeatedly reverses its direction - flows one way then the other way in successive cycles - used for powering a light in your home because the mains electricity is an a.c. Supply

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3
Q

What does a mains circuit involve?

A

A live wire which is alternately positive and negative every cycle, and a neutral wire at zero volts

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4
Q

What is the job of step-up transfomers?

A

Used at power stations to transfer electricity to the national grid - used to make the size of the alternating potential difference much bigger typically from 25,00 V to about 132,000V - decreases the current

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5
Q

What is the job of step-down transfomers?

A

Used to supply electricity from the national grid to consumers - decreases the volatge and increases the current

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6
Q

what is mains frequency?what is the value of the uks?

A

The number of cycles an alternating current passes through each second - uks main frequency is 50 cycles per second or 50Hz

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7
Q

Why is the national grids potential difference (voltage) made very high when transporting electric?

A

Means less current is needed to transfer the same amount of power - so the power loss due to the resistance heating in the cables is much reduced

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8
Q

Equation for working out the frequency of an a.c. Supply?

A

Frequency = 1 / time taken for 1 cycle

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9
Q

What is the national grid?

A

the network of cables and transformers that transport electricity from the power stations in Britain

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10
Q

Voltage of uk main electricity supply?

A

230V

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11
Q

What is the live wire? what colour is the wire?

A

Carries the alternating potential difference (voltage) from the supply - coloured brown

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12
Q

What is the neutral wire? What colour is it?

A

Neutral wire completes the circuit - earthed at the local electricity substation - at zero volts - the colour of the wire is blue

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13
Q

What is the earth wire? what colour is it?

A

Is a safety wire to stop the appliance becoming live which could electrocute you - the colour of the wire is green with yellow stripes - it is at zero volts and carries a current only if there is a fault

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14
Q

What materials are sockets and plugs made of? Why?

A

Made up of stiff plastic materials that enclose the electrical connections - plastic is used because it is a good electrical insulator

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15
Q

Describe the structure of a mains cable?

A

Made up of two or three insulated copper wires surrounded by an outer layer of flexible plastic material - copper is used because it is a good electrical conductor and bends easily

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16
Q

What is the earth wire connected to?why is it needed?

A

Connected to the longest pin in a plug and is used to earth the metal case of a mains appliance - which stops the metal case becoming live and electrocuting you

17
Q

Why do plugs contain a fuse?

A

Plugs contain a fuse between the live pin and the live wire - if too much current passes through the wre in the fuse, it melts and uts the live wire off

18
Q

What are the pins on a plug made of? Why?

A

Pinds are made of brass because it is a good conductor and doesn’t rust or oxidise and is harder the copper

19
Q

State the equation for power, P?

A

Power, P = energy transferred, E / time, t

20
Q

State the units for the equation linking power, energy transferred and time equation?

A
  • Power, P = watts
  • Energy transferred, E = joules
  • Time, t = seconds
21
Q

State the equation that links power supplied, P with current and potential difference?

A

Power supplied = current x potentital difference

22
Q

What are the units for power supplied, current and potenital difference?

A
  • Power supplied, P = watts (W)
  • Current, i = amperes (A)
  • Potential difference = volts (V)
23
Q

Example of 3 fuses ratings?

A
  • 3 A
  • 5 A
  • 13 A
24
Q

State the equation that links power,P with current and resistance?

A

Power, P = (current ^2) x resistance

25
Q

State the units for the equation linking power, resistance and current?

A
  • Power, P = W
  • Current^2 = A
  • Resistance = Ω
26
Q

State the equation that links charge flow, current and time?

A

Charge flow = current x time

27
Q

State the units for the equation that links charge flow , current and time?

A
  • Charge flow - coulombs, C
  • Current - amperes, A
  • Time - seconds, s
28
Q

Why does a resistor heat up - mention electrons and energy stores?

A

When a resistor is connected to a battery - work is done by the batter to make electrons pass through the resistor - each electron repeatedly collides with the vibrating metal ions of the resistor transferring energy to the ions - so the ions of resistor gains kinetic energy and vibrate even more - causes the resistor to become hottor

29
Q

State the equation for energy transferred when given power?

A

Energy transferred = power x time

30
Q

State the units for the equation linking energy transferred, time and power?

A
  • Energy transferred, E - joules (J)
  • power, P - watts (W)
  • time, t - seconds (s)
31
Q

State the equation that links power, current and potential difference?

A

Power, P = current x potential difference

32
Q

State the units for the equation linking power, current and potential difference?

A
  • power,P - watts (W)
  • Current,I - amperes (A)
  • Potential difference,V - volts (V)
33
Q

Equation for efficiency?

A

Efficiency = (output power/input power) x 100

34
Q

Why are elctrical appliances never 100% efficient?

A

There is always waste energy because the current in both the wire and components of the appliance has a heating effect due to the resistance of the wires and the components - energy is transferred to the surroundings - which causes the temperature to increase

35
Q

Why are elctrical appliances with moving parts never 100% efficient?

A

Electrical devices with moving parts like motors waste energy due to the firction between the moving parts which heats them up and transfers energy to the surrounings

36
Q

Explain how transformers increase the pd?

A

Step-up transfomer - has more turns on the secondary coil than the primary coil as the pd is increased the current is decreased

GCSE Physics (25 decks)

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