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Physics (GCSE Combined Science AQA: Trilogy) > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is the diagram for a fuse?

A
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2
Q

What is the circuit symbol for a diode?

A
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3
Q

What is the circuit symbol for a thermistor?

A
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4
Q

What is the circuit symbol for a variable resistor?

A
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5
Q

What is the circuit symbol for a light dependent resistor?

A
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6
Q

What is electric current?

A

The rate of flow of electrical charge.
In metal wires this charge is carried by electrons.

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7
Q

How is current measured?

A

Through an ammeter connected in series with the component.

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8
Q

What must a circuit be for an electrical charge to flow?

A

A closed circuit.

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9
Q

What is a coulomb?

A

The charge that passes a point in a circuit when there is a current of one ampere for one second.

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10
Q

What is resistance?

A

A measure of how hard it is for charge to flow through a component or a material.

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11
Q

Explain why the resistance in a wire changes as the wire gets hotter.

A

As the wire gets hotter the atomic vibrations are larger so electrons collide with atoms more frequently and the resistance increases.

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12
Q

Required Practical 15: Investigating resistance

A
  • Set up a circuit to measure the potential difference and current for a wire at different lengths along the wire
  • Calculate the resistance using R = V / I
  • Plot a graph : Resistance is directly proportional to length
    _Sources of error_:
  • Heating effect of the wire - use a low potential difference and only turn current on briefly and allow it to cool between readings
  • Measuring the length between the crocodile clips consistently
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13
Q

What are Ohmic conductors?

A

At a constant temperature, the resistance stays constant when the current changes.

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14
Q

What is the graph for a filament lamp?

A

Non-ohmic

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15
Q

What is the graph for a diode?

A

Non-ohmic

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16
Q

What is the basic circuit for measuring the resistance of a component?

A
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17
Q

What is the graph for a thermistor?

A
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18
Q

What is a thermistor used for?

A

Temperature sensors in fire alarm systems.
Thermostats fur switching on devices at certain temperatures.

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19
Q

What is the graph of an LDR?

A
20
Q

What are LDRs used for?

A

Security and street lamps.

21
Q

Required Practical 16: Investing I-V characteristics of components

A
  • Set up the circuit for each component
  • Adjust the variable resistor and record sever pairs of ammeter and voltmeter readings in a table
22
Q

Compare potential difference, current and resistance in a series and parallel circuit.

A

Series:
- Potential difference is shared: Vcell = V1 + V2
- Current is same through each lamp: I1 = I2
- Total resistance is is the sum of the resistance of each lamp
Parallel:
- Potential difference across each lamp is the same: Vcell = V1 = V2
- Total current is the sum of the current through each lamp: Itotal = I1 + I2
- The total resistance is less than the resistance of the component with the smallest resistance in the circuit

23
Q

What is a direct current?

A

The electrons move from the negative terminal to the positive terminal and the current is always in the same direction.

24
Q

What is an alternating current?

A

The direction of the movement of the electrons is constantly changing. This means the potential difference is also constantly changing.

25
Q

What is the pd-time graph for dc?

A
26
Q

What is the pd-time graph for ac?

A
27
Q

Describe the energy supply of the UK.

A

Frequency of 50 Hz and pd of 230 V

28
Q

What devices use a dc supply?

A

Mobile phone, electric toothbrush, remote control, hand held vacuum cleaner.
Devices that use a battery or cell, not the mains supply.

29
Q

What is the colour, potential difference with the Earth and purpose of the Earth wire?

A

Green and yellow stripes
0 V
Safety wire, only carries a current if there is a fault

30
Q

What is the colour, potential difference with the Earth and purpose of the Live wire?

A

Brown
230 V
Carries the alternating current from the supply, connects to a fuse.

31
Q

What is the colour, potential difference with the Earth and purpose of the Neutral wire?

A

Blue
Around 0 V
Completes the circuit.

32
Q

What dues the fuse contain?

A

A wire that will melt if the current gets too high.

33
Q

What happens if a person touches a live wire?

A

The current travels through them to the ground and they get an electric shock.

34
Q

What is the Earth wire?

A

A safety wire to stop the actual appliance becoming live if the live wire touches a conducting part of the appliance.

35
Q

What are two dangers of using the mains supply?

A

Electric shock from contact with a live connection
Fire caused by too much current

36
Q

Why is different coloured insulation used in a three-core cable?

A

To identify the different wires, to connect wires correctly for safety and for the appliance to work.

37
Q

Draw what a three-core cable looks like.

A
38
Q

An electrical appliance transfers more energy if it:

A
  • Has a higher power rating
  • Is switched on for more time
39
Q

What is the difference between dc and ac in terms of where they transfer energy from?

A

Dc supply transfer from cells and batteries whilst an ac supply transfers from the mains.

40
Q

What is electrical work?

A

How energy is transferred when charge flows in a circuit.

41
Q

Give an example of a device that transfers energy by:
a). Kinetic energy
b). Thermal energy

A

a). Any electrical device with a spinning motor e.g. washing machine
b). Any electrical device designed to get hot e.g. Hairdryer

42
Q

What is the National Grid?

A

The system of cables and transformers in the UK that links power stations to consumers.

43
Q

What are step-up transformers used for?

A

To increase the potential difference from the power stations.

44
Q

What are step-down transformers used for?

A

To decrease the pd from the transmission cables so it’s much lower for use in homes.

45
Q

Why is the National Grid system an efficient way to transfer energy?

A

A step up transformer steps up the pd and reduces the current so reducing the current reduces the energy dissipated by the current heating effect. In addition, wires with low resistance are also used to help minimise the energy dissipated.

Physics (GCSE Combined Science AQA: Trilogy) (7 decks)

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