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GCSE Physics - Edexcel Paper 2 > Electricity and Circuits > Flashcards

Electricity and Circuits Flashcards

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1
Q

What is the purpose of a cell or battery?

A

To provide potential difference (voltage).

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2
Q

What is the purpose of a switch?

A

To switch the current on or off.

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3
Q

What is the purpose of a voltmeter?

A

Measures the potential difference across a component.

- Measured in volts (V)

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4
Q

What is the purpose of an ammeter?

A

Measures the current flowing through a component.

- Measured in amps (A)

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5
Q

What is the purpose of a fixed resistor?

A

Provides a fixed resistance to the current.

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6
Q

What is the purpose of a variable resistor?

A

Provides a resistance that can be manually controlled.

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7
Q

What is the purpose of a filament lamp, or bulb?

A

It converts electrical energy into light energy.

- The filament heats up and glows

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8
Q

What is the purpose of a motor?

A

It converts electrical energy into kinetic energy.

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9
Q

What is the purpose of a diode?

A

It allows current to flow in only one direction.

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10
Q

What is the purpose of a thermistor?

A

It decreases resistance when the temperature increases.

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11
Q

What is the purpose of an LDR?

A

It decreases resistance when light intensity increases.

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12
Q

What is the purpose of an LED?

A

It gives out light when current flows through it.

- It is a diode

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13
Q

What are the two types of circuits?

A
  • Series (one loop)

- Parallel (multiple loops)

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14
Q

What rule(s) does potential difference follow in a parallel circuit?

A

That every junction will receive the same amount of voltage (it is not split across junctions).
The potential difference only splits if there is more than one component in the branch.

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15
Q

What rule does current follow in a parallel circuit?

A

That the sum of the currents across all of the branches must equal the current leaving the cell and going back to the cell.

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16
Q

What should you always assume when current is split in a parallel circuit?

A

That it is split evenly across the junctions unless stated otherwise.

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17
Q

What should you always assume when the potential difference is split across components in a circuit?

A

That it is split evenly across components unless stated otherwise.

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18
Q

What is ‘charge’?

A

A charge is the number of electrons in a circuit.

- It is measured in coulombs (C)

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19
Q

What is the equation to find the charge in a circuit?

A

Charge (C) = Current (A) x Time (s)

Q = I x t

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20
Q

What is the equation to find the energy transferred in a circuit in relation to charge and potential difference?

A

Energy (J) = Charge (C) x Potential difference (V)

E = Q x V

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21
Q

What does Ohm’s law state?

A

The current through a component relates to its resistance and the potential difference across it.

22
Q

If resistance is higher, what is the current?

A

Smaller.

23
Q

What is the equation for Ohm’s law?

A

Voltage (V) = Current (A) x Resistance (Ω)

V = I x R

24
Q

What rules does current and potential difference follow across resistors in a series circuit?

A
  • The current through each resistor is the same value.

- The sum of the voltages across the resistors must add to equal the cell voltage.

25
Q

What rules does current and potential difference follow across resistors in a parallel circuit?

A
  • The total current leaving the battery is equal to the sum of the current flowing in the separate branches.
  • The potential difference across the resistors in each branch is equal to the potential difference of the battery.
26
Q

What does an I-V graph show?

A

How the current flowing through a component varies as the potential difference across it varies.

27
Q

For a fixed resistor, describe the I-V graph.

A
  • The temperature remains constant so the resistance remains constant.
  • Current is directly proportional to the potential difference.
  • The slope/gradient remains straight constantly.
28
Q

For a filament lamp, describe the I-V graph.

A
  • When potential difference increases, so does temperature which increases atomic vibrations.
  • Increased temperature leads to increased resistance.
  • The slope/gradient decreases as the potential difference increases.
29
Q

For a diode, describe the I-V graph.

A
  • The line is initially flat because there is a threshold in the forward direction; current only flows in one direction in a diode.
  • The resistance does not change when current and potential difference increase.
  • However, a diode has a very high resistance in the reverse direction.
30
Q

According to what factors does the resistance in an LDR and thermistor change?

A
  • Light conditions (LDR)

- Temperature (Thermistor)

31
Q

Describe the resistance graph of an LDR.

A
  • Resistance depends on light intensity
  • LDR’s have a high resistance in the dark
  • As light intensity increases, the resistance decreases.
32
Q

Describe the resistance graph of a thermistor.

A
  • Resistance depends on the temperature
  • Thermistors have a high resistance in low temperatures
  • As temperature increases, resistance decreases.
33
Q

What is the heating effect in a circuit?

A

Components and wires increase in temperature because electrical energy is dissipated as thermal energy into the surroundings when the current is doing work against a resistance.
- Collisions between the electrons and the metal ions in the lattice lead to kinetic energy being dissipated as thermal energy.

34
Q

What are the advantages/uses of the heating effect?

A
  • Heating water in a kettle
  • Radiant heaters
  • Toasters, grills, and ovens
  • Underfloor heating
35
Q

What are the disadvantages of the heating effect?

A
  • Appliances can catch on fire
  • Users can be burned
  • Wasted energy (lower efficiency)
36
Q

What equation is used to calculate the energy transferred by a device depending on how long it has been turned on for?

A

Energy (J) = Current (A) x Potential difference (V) x Time (s)
E = I x V x t

37
Q

What is the equation to calculate electrical power that is dependent on the current and potential difference?

A

Power (W) = Current (A) x Potential difference (V)

P = I x V

38
Q

What is the equation to calculate the electrical power that is dependent on the current and resistance?

A

Power (W) = Current² (A) x Resistance (Ω)

P = I² x R

39
Q

What is d.c and what happens?

A
  • D.c is a direct current
  • Direct current is in a wire
  • The electrons all flow in the same direction
40
Q

What is a.c. and what happens?

A
  • A.c is alternating current
  • Electricity supplied to homes and businesses is an alternating current.
  • The direction of the current changes regularly, therefore the potential difference is constantly changing.
41
Q

How is d.c. provided?

A

In a cell or battery.

42
Q

How is a.c. provided?

A

The mains supply.

43
Q

At what voltage does mains electricity enter UK homes?

A

230V a.c.

44
Q

What are the components inside a mains plug?

A
  • Earth wire
  • Live wire
  • Neutral wire
  • Fuse
45
Q

What colour is the Earth wire and what purpose does it have?

A
  • It is yellow and green in colour.

- It acts as a safety feature in the plug (keeps the electrical current earthed or grounded to prevent electric shocks.

46
Q

What colour is the neutral wire and what purpose does it have?

A
  • It is blue in colour.
  • It completes the circuit with the appliance.
  • It is at a potential difference of 0V.
47
Q

What colour is the live wire and what purpose does it have?

A
  • It is brown in colour.
  • It carries the supply to the appliance.
  • It is at a potential difference of 230V.
48
Q

What is the purpose of the fuse?

A
  • It connects to the live wire
  • It contains a wire that will melt if the voltage is too high.
  • If the fuse blows, the device will be at 0V and not at 230V.
49
Q

Name three safety features used in electrical components and circuits?

A
  • Earthing
  • Circuit breakers
  • Fuses
50
Q

What is the purpose of earthing?

A

It provides a path for a fault current to flow into the earth.

51
Q

What is the National Grid?

A

A system of wires that transmits electricity from power stations to where the electricity is needed and used.

52
Q

Explain the process of the National Grid.

A

1) Fossil fuels or nuclear fuel is used to generate electrical energy in the power station.
2) A step-up transformer will increase the voltage to 132kV or more. The electrical energy is transmitted at a high voltage and a low current through the wires to reduce energy losses as heat. It also allows for thinner wires and reduced costs.
3) A step-down transformer will decrease the voltage for safer use inside our homes and industries (230V)

GCSE Physics - Edexcel Paper 2 (7 decks)

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