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GCSE Physics > Topic 10 - Electricity & Circuits > Flashcards

Topic 10 - Electricity & Circuits Flashcards

(86 cards)

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1
Q

What 3 subatomic components make up an atom?

A

Electrons
Protons
Neutrons

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2
Q

Describe the structure of an atom

A

Neutrons and protons in nucleus

Electrons surrounding nucleus in shells

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3
Q

What are the charges of the particles in an atom

A

Proton +1
Neutron 0
Electron -1

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4
Q

In a closed circuit, if there is a potential difference in the circuit there will also be a…

A

Current

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5
Q

How is current defined

A

As the rate of flow of charge (or electrons) round a circuit

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6
Q

What are the units of charge

A

Coulombs (C)

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7
Q

What are the 2 ways that a component can be connected in a circuit

A

Series (same loop)

Parallel (adjacent loop)

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8
Q

Voltage is also known as…

A

Potential difference

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9
Q

How does the potential difference across 2 components vary when connected in series and parallel?

A

In series circuit, total PD is shared between each component

In parallel circuit, PD across each component is the same

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10
Q

If 2 resistors are connected in parallel, what can be said about their combined total resistance

A

Total resistance is less than the smallest of the 2 individual resistances

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11
Q

If 2 resistors are connected in series, what can be said about their total resistance

A

Their total combined resistance is equal to the sum of the two indiviso resistances

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12
Q

Where must a voltmeter be placed in a circuit

A

In parallel with the component that is being measures

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13
Q

Give an equation relating potential difference with energy transferred and charge

A

Potential difference (V) = energy transferred (J) / charge (C)

V = E/Q

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14
Q

A volt can also be described as…

A

Joule per coulomb

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15
Q

What is an electric current

A

The rate of flow of charge

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16
Q

State the equation linking charge, current and time. Give the units for the quantities involved

A

Q = I t

Charge(coulombs), Current(amperes), Time(secs)

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17
Q

What can be said about the value of current at any point in a single closed loop?

A

Current is the same at all points in a closed loop

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18
Q

What 2 factors does the current in a circuit depend on?

A 
Potential difference (V)
Resistance (R)
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19
Q

What equation supuld be used to calculate potential difference if current and resistance are known?

A 
V = I R
Potential difference (V) = Current (A) x Resistance (Ohms)
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20
Q

Whats an ammeter and where must it be connected in a circuit?

A

Measures current.

Placed in series with component its required to measure.

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21
Q

What happens when current reaches a junction in a circuit?

A

Current is conserved.

The total current remains the same and is split between the two branches.

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22
Q

How does resistance affect current in a circuit?

A

As the total resistance of a circuit increases, the current flowing through the circuit decreases

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23
Q

How can the current in a circuit be varied

A

Using a variable resistor

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24
Q

Give the equation linking current with resistance

A

P.D. (V) = current (A) x resistance (Ohms)

V = I R

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25
How is total resistanve affected by 2 resistors in series
Total resistance increases | Is equal to the sum of 2 resistors
26
How is total resistance affected by 2 resistors in parallel
Total resistance decreases | Is less than the resistance of the resistor with lowest resistance
27
Whats an Ohmic Conductor. State conditiom required.
Conductor for which current and pd are directly proportional Resistance remians constant as current changes Temp must be constant
28
List 4 components for which resistance isnt constant as current changes
Filament lamps Diodes Thermistors Light dependant resistors (LDRs)
29
What happens to resistance of a filament lamp as the temperature increases? Why?
Resistance increases Metal ions have more kinetic energy so vibrate more, colliding more frequently with electrons as they flow through metal This creates more resistance to current flow
30
Whats different about current flow through a diode?
Current only flows in one direction | Resistance is very high in other direction, preventing current flow
31
State what happens to the resistance of a thermistor as temperature increases
The thermistors resistance decreases
32
Give 2 examples of when a thermistor may be used
In a thermostat to turn a heater on below a certain temp | In a freezer to turn on a cooler when the temp becomes too high
33
State what happens to the resistance of an LDR as light intensity decreases
The LDRs resistance increases
34
Give an application for a LDR
Street lamps or night lights | When light levels drop (night) resistance increases and the light gains sufficient current to turn on
35
How do diodes work?
A diode only allows current to flow in one direction. If current is flowing right way, resistance is large for small voltages (uo until 0.6V) but then higher voltages become very small.
36
What electrical component does this graph represent? —|-/
Diode
37
What factors affect the energy transferred when charge flows through a component?
Amount of charge | Pd across the component
38
Give an equation linking energy, current and pd
Energy (J) = pd (V) x current (A) x time (s) | E = V I t
39
Define potential difference in terms of charge
The work done per unit charge
40
Give an equation relating potential difference to charge
``` Energy transferred (J) = charge (C) x pd (V) E = Q V ```
41
When an electrical current flows through a resistor why does it heat up?
There are collisions between the electrons and ions in the resistors lattice. This causes a transfer of kinetic energy into thermal energy, which is released into the surroundings.
42
How do low resistance wires reduce unwanted energy transfers
A smaller resistance will mean there are fewer collisions, therefore less energy will be wasted through heating
43
What are some advantages of the heating effect
Its useful for appliances such as toasters or electrical fires, where the heat is the desired product
44
What are some disavantages of the heating effect
Loss of energy as heat energy can make an appliance inefficient If an appliance overheats it can catch fire or overheat which could ruin the device or injure user
45
The energy transferred per second is also known as
Power
46
Define power
The rate of energy transfer, or rate at which work is done
47
What are the units of power
Watts W
48
Give equation linking power and pd
Power (W) = current (A) x pd (V) | P = I V
49
Give equation to work out power without pd
Power (W) = current squared (A) x resistance (Ohms) | P = I2 R
50
Give an equation linking power and energy
Power (W) = energy (J) / time (s) | P = E/t
51
Give both equations linking power with resistance
Power (W) = current squared (A) x resistance (Ohms) P = I2 x R Power (W) = pd squared (V) / resistance (Ohms) P = V2 / R
52
What word describes materials that electricity will pass through?
Conductors
53
What word describes materials that electricity cannot pass through?
Insulators
54
What components do you need to make a circuit that would make a small torch bulb light up?
Battery, connecting wires, lamp, switch is optional
55
What are the two terminals of an electric cell labelled as?
Plus and minus
56
In an electric circuit with a battery, which of these materials will conduct: copper, wood, salty water
Copper and salty water
57
Which of these materials are insulators? Plastic metal air
Plastic and air
58
What name is given to the negatively charged subatomic particles that cause an electric current?
Electrons
59
Is mains voltage about 15 times, 150 times or 1500 times bigger than the voltage from a battery?
About 150 times
60
If you connect some cells together in series, what forms
A battery
61
Which line on the cell is the negative terminal
Shorter line
62
Whats the difference between convectional current and flow of electrons?
Electrons flow from negative terminal of cell to positive terminal, convectional flows the other way
63
What 2 conditions are needed to give a current in a circuit?
Closed circuit and potential difference
64
What is current measured in
Amps/amperes
65
What does AC mean?
Alternating current
66
What is alternating current?
Current which is constantly changing between a negative and positive maximum
67
What does DC mean?
Direct current
68
What is direct current?
Current which takes a constant value
69
Is mains electricity an AC or DC supply?
AC supply
70
What is meant by the frequency of a supply?
The rate at which an AC current changes
71
Whats the frequency and voltage of the UK mains electricity supply?
Frequency: 50Hz Voltage: 230V
72
What type of current do batteries and cells supply?
Direct current
73
What is the power rating of an appliance?
Shows how much energy a device converts per second
74
What wires does a typical domestic appliance have?
Live wire Neutral wire Earth wire
75
What colour is the live wire?
Brown
76
What colour is the neutral wire?
Blue
77
What colour is the earth wire?
Green and yellow stripes
78
Explain when the Earth wire does and doesnt carry a current
Under normal circumstances, no current flows through wire | Current flows when a fault occurs in the appliance
79
What potential is the neutral wire at?
0 volts
80
State the potential dofference between the live and earth wires
230 volts
81
What is the purpose of the neutral wire?
To complete the circuit by connecting the appliance back to the mains supply
82
For metal appliances, where is the earth wire connected to? Why?
Metal casing of appliance | If live wire touches the casing, current will flow through earth wire preventing electrocution
83
How does a fuse stop a device getting damaged?
When current gets too high fuse wire melts and breaks stopping current flowing to appliance preventing damage
84
Why is it important to connect a fuse or switch to live wire
When switch turned off/fuse breaks it will break the circuit and stop current flowing through wire. This provides a method to stop current flowimg into the appliance.
85
Why is it dangerous to have a connection between the earth wire and live wire?
Can result in current surge, causing electrical shocks
86
What is a current surge?
When significantly more current comes through the wire

GCSE Physics (6 decks)

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