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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is current

A

The flow of charge

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2
Q

What is a series circuit

A

It has no branches and current can only flow in one path

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3
Q

What is used to measure current in a circuit

A

Ammeter

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4
Q

Describe current in a series circuit

A

Current is the same in a series circuit

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5
Q

What’s a parallel circuit

A

A circuit that contains branches

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6
Q

Explain current in a parallel circuit

A

The total current through the whole circuit is the sum of the currents through the separate components

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7
Q

What is potential difference

A

How many joules of energy is transferred for each coulomb of charge

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8
Q

How is potential difference measured

A

Using a voltmeter

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9
Q

Describe the potential difference in a series circuit

A

The total potential difference of the power supply is shared between the components

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10
Q

Describe potential difference in a parallel circuit

A

The potential difference across each component is the same

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11
Q

What is a battery

A

2 or more cells connected together

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12
Q

What is charge measured in

A

Coulombs (C)

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13
Q

Equation for charge

A

Q(C) = I(A) x t(s)

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14
Q

What is the equation that links potential difference, charge, energy transferred

A

E(J) = Q(C) x V(V)

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15
Q

What is resistance

A

It tells us The potential difference required to drive a current through a component

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16
Q

If there is a large resistance what happens to current

A

Smaller current

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17
Q

Equation linking potential difference, current, resistance

A

R(ohm) = V(V)/I(A)

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18
Q

What is a resistor

A

It adds resistance into a circuit

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19
Q

Describe the current in an ohmic conductor

A

The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes.

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20
Q

Describe the resistance in components such as lamps, diodes, thermistors, and LDR’s

A

The resistance is not constant as it changes with the current through the component

21
Q

Describe the resistance in a filament lamp

A

The resistance of a filament lamp increases as the temperature of the filament increases

22
Q

Describe the current in a diode

A

The current through a diode flows through one direction only
The diode has a very high resistance in the reverse direction

23
Q

Describe the resistance in a series circuit

A

The total resistance of two components is the sum of the resistance of each component

24
Q

Describe the resistance in a parallel circuit

A

The total resistance of two resistors is less than the resistance of the smallest individual resistor

25
Q

Describe the resistance of an LDR

A

the resistance of the LDR decreases as light intensity increases
This is because current flows through the LDR when there is light

26
Q

Describe the resistance of a thermistor

A

The resistance of a thermistor decreases as the temperature increases

27
Q

What are thermostats

A

Devices that turn appliances on or off depending on the temperature

28
Q

What is the equation linking power, energy, time

A

E(J) = P(W) x t(s)

29
Q

What is power

A

The rate at which energy is transferred

30
Q

What is direct current (DC)

A

Electrons only travel in one direction

31
Q

What is alternating current (AC)

A

Current is constantly changing direction

32
Q

Benefit of using AC

A

It’s very easy to use a transformer to increase or decrease the potential difference

33
Q

What is mains electricity frequency

A

50Hz

34
Q

What is the potential difference of mains electricity

A

230 volts

35
Q

What are the three core cables in mains electricity

A

Live wire
Neutral wire
Earth wire

36
Q

What color is the live wire

A

Brown

37
Q

What color is the neutral wire

A

Blue

38
Q

What color is the earth wire

A

Green and yellow stripes

39
Q

Function of the live wire

A

Carries the alternating potential difference from the supply

40
Q

Function of the neutral wire

A

Completes the circuit

41
Q

Function of the earth wire

A

The earth wire 0 V
It only carries a current if there is a fault

42
Q

Why is the live wire dangerous

A

If touched the live wire can be fatal
This is because it still has a potential difference of 230 V
So a current would flow through the person into the earth and they would be electrocuted

43
Q

Explain how the earth wire prevents an electric shock

A

The earth wire is connected to the ground
If the case becomes live, a huge current flows to earth
The fuse melts and shuts off the current
This prevents anyone from getting an electric shock from touching the case

44
Q

What does a step up transformer do

A

Electricity passes through step up transformers which increase the potential difference to several hundred thousand volts
This is so less energy is lost in the power cables when the potential difference is very high

45
Q

What does a step down transformer do

A

The electricity passes through step down transformers which reduce the potential difference to around 230 V
This is a safe voltage to pass onto homes

46
Q

What is the national grid

A

A system of transformers and cables

47
Q

Describe how electrons move from a plastic rod to a cloth when rubbed together

A

Cloth is an insulator with electrons
Plastic is also an insulator
When a plastic rod and cloth is rubbed together electrons move from the plastic onto the cloth
So the cloth now has an overall negative charge
The plastic now has an overall positive charge as it’s lost electrons

48
Q

What happens to objects with opposite charges

A

They attract as there is a force of attraction

49
Q

What happens to objects with the same charge

A

The have forces of repulsion so repel

Physics (7 decks)

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