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Nat 5 Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

Current is

A

Amount of charge that passes a point each second
Q
I = –
s

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2
Q

Voltage is

A

The energy given to each charge

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3
Q

Resistance is

A

The opposition of current

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4
Q

Power is

A

Energy used per second

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5
Q

The unit of current is

A

Amperes A

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6
Q

The unit of voltage is

A

Volts V

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7
Q

The unit of resistance is

A

Ohms Ω

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8
Q

The unit of power is

A

Watts W

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9
Q

The unit of energy is

A

Joules J

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10
Q

The unit of charge is

A

Coulombs C

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11
Q

Voltage across components in series

A

Is shared, adds up to the supply voltage

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12
Q

Current in series components is

A

The same

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13
Q

Voltage across components in parallel is

A

The same

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14
Q

Current in parallel components

A

Is split, adds up to the supply current

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15
Q

The relationship between current, voltage and resistance is

A

V = IR

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16
Q

The relationship between power, current and voltage is

A

P = IV

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17
Q

The relationship between power, current and resistance is

A

P = I^2 R

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18
Q

The relationship between power, voltage and resistance is

A

V^2
P = —
R

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19
Q

The combined resistance of resistors in series is given by the relationship

A

Rt = R1 + R2 + …

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20
Q

The combined resistance of resistors in parallel is given by the relationship

A

1 1 1
— = — + — + …
Rt R1 R2

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21
Q

Graph of a wave is

A

Alternating current (a.c.)

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22
Q

What is AC.

A

A current whose instantaneous value and direction varies with time.

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23
Q

Graph is a horizontal line which is

A

Direct current (d.c.)

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24
Q

In alternating current the current

A

Reverses direction every fraction of a second

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25
Q

In direct current the current

A

Is always in the same direction

26
Q

To measure the current in a component an ammeter is connected

A

In series with the component

27
Q

To measure the voltage across a component a voltmeter is connected

A

In parallel with the component

28
Q

The purpose of a fuse is

A

to protect wiring from overheating by breaking when too much current passes through them

29
Q

The general rule for fuse choice based on the power rating of an appliance is

A

3A fuse for appliances with a power rating up to
720 W
13A fuse for appliances rated over 720 W

30
Q

The energy change in a motor is

A

electrical to kinetic

31
Q

The energy change in a lamp is

A

electrical to light (and heat)

32
Q

The energy change in a loudspeaker is

A

electrical to sound

33
Q

The energy change in a microphone is

A

sound to electrical

34
Q

The purpose of a relay is

A

to allow low voltage electronic circuits to switch on and off appliances that operate at higher voltages

35
Q

The function of a diode is

A

to only allow current in one direction

36
Q

The energy change in an LED is

A

electrical to light

37
Q

A resistor is connected in series with an LED to

A

prevent damage to the LED

38
Q

Increasing the resistance (connected in series circuit, battery, resistor, capacitor)

A

increases the time taken to charge the capacitor

39
Q

Increasing the capacitance (connected in series circuit, battery, resistor, capacitor)

A

increases the time taken to charge the capacitor

40
Q

The function of a transistor is

A

as an electronic switch

41
Q

In a voltage divider, the relationship between the resistances (R1 and R2) and the voltages across the resistors (V1 and V2) is

A

the ratio of the voltages is equal to the ratio of
resistances
or
𝑉1 𝑅1
— = —
𝑉2 𝑅2

42
Q

In a voltage divider, the relationship between the resistances (R1 and R2), the supply voltage(Vs) and voltage across a resistor (V2) is

A

𝑅1
𝑉 = ———– x 𝑉s
𝑅1 + 𝑅2

43
Q

What happens if a positive and a negative charge are brought together?

A

They attract each other

44
Q

Name one source of AC

A

Mains supply

45
Q

What happens if two positive charges are brought together?

A

They repel each other

46
Q

What is a Light Dependent Resistor?

A

A resistor whose resistance changes with changes in light level

47
Q

What would happen to an electron being fired through the electric field between 2 plates?

A

It would experience a force and be attracted to the positive plate.

48
Q

How does a relay work?

A

Close a switch to make a current flow in a wire.
This creates an electromagnet.
Electromagnet attracts metal switch.
This completes the second circuit and the lamp switches on.

49
Q

What will be the voltage across a capacitor when it is fully discharged?

A

Zero volts.

50
Q

What happens if you increase the resistance in a circuit?

A

The current will decrease

51
Q

What is DC?

A

Direct current. Electrons move in one direction only.

52
Q

What would the field lines around a positive point charge look like?

A

Field lines show direction away from the positive point charge

53
Q

How can you identify a series circuit?

A

It is a circuit with only one path round it.

54
Q

Name one source of DC

A

Battery

55
Q

How should a diode or LED be connected with a battery to light correctly?

A

Small line on battery points to small line on LED or diode.

56
Q

Explain how a fuse works.

A

A fuse is a thin wire. If too much current passes through it, it will get hot and melt. This breaks the circuit.

57
Q

What is electric charge?

A

An electric charge occurs when there are fewer or more electrons than protons.

58
Q

If you heat a conductor, what happens to it’s resistance?

A

It increases

59
Q

What does an electric field line show?

A

The direction a positive charge would move in that field.

60
Q

State what is meant by AC?

A

Alternating current. The electrons change direction, moving backwards and forwards, many times in a second.

Nat 5 Physics (6 decks)

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