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Physics > Topic 2 Electricity > Flashcards

Topic 2 Electricity Flashcards

1
Q

Total resistance =

A

R1 + R2 etc.

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2
Q

What colour is the earth wire and what does it do?

A

Green and yellow, safety wire to stop the appliance becoming live, at 0V if running smoothly

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3
Q

What colour is the neutral wire and what does it do?

A

Blue, completes the circuit, around 0V

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4
Q

What colour is the live wire and what does it do?

A

Brown, carries the alternating potential difference from the supply, p.d. between live and earth wire is 230V

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5
Q

What is the cells function and symbol? 1

A

pushes the electrons around a complete circuit

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6
Q

What is the switches function and symbol? 2

A

enables the current to be switched on or off

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7
Q

What is the bulb/lamps function and symbol? 3

A

emits light

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8
Q

What is the fixed resistors function and symbol? 4

A

limits the current in a circuit

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9
Q

What is the variable resistors function and symbol? 5

A

allows current to be varied

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10
Q

What is the fuses function and symbol? 6

A

will melt and break if the current is too strong

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11
Q

What is the diodes function and symbol? 7

A

allows current in only one direction

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12
Q

What is the LEDs function and symbol? 8

A

emits light

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13
Q

What is the LDRs function and symbol? 9

A

decreases in resistance as light intensity increases

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14
Q

What is the thermistors function and symbol? 10

A

resistance depends on temperature

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15
Q

What is the ammeters function and symbol? 11

A

measures flow of electrons (current)

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16
Q

What is the voltmeters function and symbol? 12

A

measures electric potential difference (voltage)

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17
Q

Define current

A

Current is the rate of flow of charge

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18
Q

Charge is measured in …

A

Coulombs (C)

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19
Q

Current is measured in …

A

Ampere (A)

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20
Q

Potential difference is measured in …

A

Volts (V)

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21
Q

Resistance is measured in …

A

Ohms (Ω)

22
Q

What is ohm’s law?

A

Ohm’s law states that the current flowing through a wire is directly proportional to the voltage across it (if the temp remains constant)

23
Q

Define resistance

A

It is a measure of the opposition to the current flow in an electrical circuit

24
Q

As length of wire increases, potential difference _________, current __________ and resistance ________.

A

increases, decreases, increases

25
Q

Describe the I-V graph of a resistor

A

13, the current is directly proportional to the potential difference so you get a straight line

26
Q

Describe the I-V graph of a bulb/filament lamp

A

14, current and p.d are proportional to begin with - as the current increases, the temp increases and so the resistance increases. This means less current can flow so the graph curves and plateaus.

27
Q

Describe the I-V graph of a diode

A

15, the current will only flow in one direction so the diode has a very high resistance in one direction.

28
Q

Describe the LDR graph

A

16, the darker it is, the more resistance there is

29
Q

Describe the Thermistor graph

A

17, the colder it is, the more resistance there is

30
Q

What are the three golden rules for series circuits?

A

-current is the same throughout
-potential difference of the power supply is shared between the components
-resistance is added up, Rtotal = R1 + R2

31
Q

Define potential difference/voltage

A

the difference in electrical potential between two points, the driving force that pushes electric charge around a circuit

32
Q

What are the three golden rules for a parallel circuit?

A

-current will be shared through separate components
-p.d. is the same across each component
-adding a resistor in parallel reduces the total resistance

33
Q

What is AC?

A

Alternating current - the current is constantly changing direction

34
Q

What is DC?

A

Direct current - the current only flows in one direction

35
Q

Is the electricity in your home AC or DC?

A

Alternating current (AC)

36
Q

What is the supply and frequency of the current in the mains supply?

A

230V, 50Hz

37
Q

What type of current to cells and batteries supply?

A

Direct current (DC)

38
Q

What is meant by 1 Amp in terms of charge?

A

1 coulomb of charge flows past a point every second

39
Q

What is meant by 1 Volt in terms of charge?

A

1 joule of work is done per coulomb of charge

40
Q

Define a transformer

A

Increase and decrease voltage at particular stages in the National Grid

41
Q

Describe how step-up transformers are used in the National Grid system

A

A step-up transformer is used after the power station to increase the potential difference which then in turn decreases the current. This means less energy is wasted through thermal heat so it improves efficiency.

42
Q

Describe how step-down transformers are used in the National Grid system

A

Step-down transformers are used to bring the voltage back down to 230V so it is safe to use at home

43
Q

Like charges ______

A

repel

44
Q

Unlike charges ______

A

attract

45
Q

Insulating materials that lose electrons when rubbed become __________ charged

A

positively

46
Q

Insulating materials that gain electrons when rubbed become __________ charged

A

negatively

47
Q

Explain why insulators don’t lose their charge

A

The electrons gained by the insulator are held by the atoms. It doesn’t conduct electricity so the electrons can’t leave

48
Q

Electric field lines go from …

A

positive to negative

49
Q

Explain how an uncharged object may become positively charged

A
  • negatively charged
  • electrons are transferred
  • from the neutral object
50
Q

How are sparks caused?

A

When there is high p.d. between a charged object and the earth

Physics (8 decks)

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