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AQA Physics [Paper 1] > P5- Domestic electricity 🔌 > Flashcards

P5- Domestic electricity 🔌 Flashcards

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1
Q

How does a blender transfer energy?

Hint: why?

A
  • electrical energy—> kinetic energy of motors because the main purpose of these appliances is to movement.
  • The blender moves to mix the food; due to friction in the motors, a small amount of thermal energy will also be generated. [not intended]
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2
Q

How does a fan transfer energy ?

Hint: thermal energy

A
  • electrical energy—> kinetic energy of motors because the main purpose of these appliances is to movement.
  • the fan moves to create air currents; due to friction in the motors, a small amount of thermal energy will also be generated. [not intended]
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3
Q

How does an iron transfer energy ?

Hint: don’t generate

A
  • electrical energy—-> thermal energy
  • electrical energy from the mains, is transferred to thermal energy- since the appliances are designed to get hot. [they don’t generate kinetic energy]
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4
Q

How does a kettle transfer energy ?

Hint: mains ac

A
  • electrical energy—-> thermal energy
  • electrical energy from the mains ac supply, is transferred to the thermal energy store, of the heating element inside the kettle.
  • since the appliances are designed to get hot. [they don’t generate kinetic energy]
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5
Q

How does a hair dryer transfer energy ?

Hint: motor

A
  • electrical energy—> kinetic energy of electric motors + thermal energy
  • This appliance uses electrical energy and it transfers electrical energy, to kinetic energy of the electric motors + thermal energy.
  • A motor moves air through the hair dryer, and the heating element heats the air.
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6
Q

How does a washing machine transfer energy ?

A
  • electrical energy—> kinetic energy of electric motors + thermal energy
  • This appliance uses electrical energy and it transfers electrical energy, to kinetic energy of the electric motors + thermal energy.
  • a heating element heats the water, and a motor turns the drum to wash the clothes.
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7
Q

RECAP: What is power ?

A
  • power is, the rate at which energy is transferred.
  • OR the rate at which work is done
  • [1W, is an energy transfer of 1J per second]
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8
Q
  • Fill in the gaps: appliances which are designed to generate ________ energy, usually have a much ______ power rating than appliances designed to generate kinetic energy.
A
  • appliances which are designed to generate thermal energy, usually have a much higher power rating than appliances designed to generate kinetic energy.
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9
Q

No appliance completely transfer all energy usefully.

The higher the current, what will happen to the energy transferred ?

A
  • the higher the current, the more energy is transferred to the thermal energy stores of the components. [and the surroundings]
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10
Q

What is direct current [dc] ?

A
  • direct current is [current from a cell or battery,] that always flows in the same direction.
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11
Q

What is alternating current [ac] ?

A
  • alternating current, is current that is constantly changing direction.
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12
Q

In the UK, what type of current is the mains electricity?

A
  • the mains electricity in the UK is alternating current.
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13
Q

What is the main benefit of using alternating current ?

A
  • the main benefit of using alternating current is:
  • it’s easier to use a transformer, to increase or decrease the potential difference, than it is with direct current.
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14
Q

What is the frequency of the UK’s domestic electricity supply ?

A
  • the frequency of the UK’s domestic electricity supply, is 50 Hz [hertz]
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15
Q

What is the potential difference of the UK’s domestic electricity supply ?

A
  • the potential difference of the UK’s domestic electricity supply is 230V.
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16
Q

What’s an oscilloscope ?

A
  • an oscilloscope is used to see the pattern of current.
17
Q

In a oscilloscope, how can we calculate the frequency

A
  • [Periodic time for one cycle [T] = divisions x timebase]
  • Frequency [F], F= 1/T
  • first work out the time from one peak, to the next peak- this shows one complete cycle.
  • look at the time interval: the time between the peak.
18
Q

How are electrical appliances in the UK, normally connected to the mains supply ?

Hint: cables

A
  • electrical appliances in the UK, normally connected to the mains supply by three core cables.
  • there are three wires that are made of copper- and copper is a good conductor of electricity; the coatings of the wires are made of plastic and they don’t conduct electricity.
19
Q

What is the defenition of ‘the live wire ?’

Hint: carries

A
  • the live wire, is the browned colour wire that carries alternating current from the supply, in a mains power supply.
20
Q

What is the neutral wire ? [3]

Hint: mains power supply

A
  • the neutral wire, is a [/the]blue coloured wire that completes the circuit in a mains power supply
21
Q

What is the definition of ‘the earth wire ?’

A
  • the earth wire, connect the metal case of an appliance to the earth in a mains cable
22
Q

Explain how the earth wire works ? [3]

Hint: metal case

A
  • the metal case of an appliance is connected into the Earth wire and the Earth wire is connected into the ground, with a metal rod.
  • This means that if the case becomes live, a huge current flows to the Earth. The fuse then melts, shutting off the current. [as it breaks the circuit]
  • This is what prevents anyone from getting an electric shock from touching the case, of an appliance [if the live wire touches it].
23
Q

If the switch is open, there can still be a risk of electric shock. Why ?

Hint: part

A
  • even if the switch is opened [e.g- plug socket or light switch turned off] the first part of the live wire running to the switch, still has a potential difference of 230V.
  • so if you made contact with the live wire, your body provides a connection between the supply and the earth- current would still flow through you.
24
Q

Why is any connection between live and earth dangerous ?

Hint: 🔥

Hint #2: huge current

A
  • any connection between live and earth dangerous, because if the connection creates a low-resistance path to the earth, a huge current flows. [this could result in a fire hazard]
25
Q

What can you tell me about direct and alternating current, in an oscilloscope

A
  • in an alternating current: the potential difference is rising and falling-this shows the current is moving backwards and forwards.
  • the height of the peak, tells us the maximum potential difference.
  • in a direct current: the potential difference doesn’t change and is therefore a flat line.
26
Q
  • Fill in the gaps: the live wire is _____ and this can be remembered by- Br [bottom right] ____ because it’s always the bottom right wire.
  • ; the live wire also carries the ___________ potential difference [of 230V], from the mains supply and is also connected to a ____ in the plug.
A
  • the live wire is brown and this can be remembered by- Br [bottom right] brown, because it’s always the bottom right wire.
  • the live wire also carries the alternating potential difference [of 230V], from the mains supply and is also connected to a fuse in the plug.
27
Q

How can the live wire be dangerous ?

Hint: 0V

A
  • the live wire can be extremely dangerous, and could easily be fatal if touched- since your body, [just like the earth] is at 0V.
  • meaning that if you touch the wire, a large potential difference [of 230V] is produced across your body, allowing a current to flow through you into the earth- which electrocutes you.
28
Q

What colour is the neutral wire ?

A
  • the neutral wire is blue and this can be remembered by- Bl [bottom left] blue, because it’s always the bottom left wire.
  • the neutral wire completes the circut, having a potential difference of 0V.
  • [when the appliance is operating normally, current flows through the live and neutral wires.]
29
Q

What colour is the earth wire ?

A

the earth wire is green-and-yellow striped. It’s a safety wire, to stop the from becoming live.

AQA Physics [Paper 1] (17 decks)

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