KO2 Electricity Flashcards
1
Q
Name the components labelled A to E.
A
A - open switch
B - closed switch
C - cell
D - battery
E - diode
2
Q
Name the components labelled F to J.
A
F - resistor
G - variable resistor
H - light-emitting diode (LED)
I - lamp
J - fuse
3
Q
Name the components labelled K to M.
A
K - voltmeter
L - ammeter
M - thermistor
N - light-dependent resistor (LDR)
4
Q
State the function of a switch.
A
To turn a circuit on and off (by allowing or not allowing current to flow).
5
Q
State the function of a cell or battery.
A
To supply energy to a circuit.
6
Q
State the difference between a cell and a battery.
A
A battery is made up of multiple cells.
7
Q
State the function of a diode.
A
To allow current to flow in one direction only.
8
Q
State the function of a resistor.
A
To limit the flow of charge.
9
Q
State the function of a variable resistor.
A
To provide a resistance that can be manually altered.
10
Q
What does LED stand for?
A
Light-emitting diode
11
Q
State the function of a LED.
A
To light up (transfer energy by radiation) whilst only allowing current to flow in one direction (as for a diode).
12
Q
State the function of a lamp.
A
To light up (transfer energy by radiation).
13
Q
State the function of a fuse.
A
To stop current flowing if it gets too large.
14
Q
State the function of a voltmeter.
A
To measure potential difference.
15
Q
Explain which of these diagrams shows a voltmeter connected correctly to measure the potential difference across the bulb.
A
B, it is in parallel with the bulb.
16
Q
State the function of an ammeter.
A
To measure electrical current.
17
Q
Explain which of these diagrams shows an ammeter connected correctly to measure the current through the bulb.
A
A, it is in series with the bulb.
18
Q
State the function of a thermistor.
A
To alter its resistance in response to the temperature of the room.
19
Q
What does LDR stand for?
A
Light-dependent resistor
20
Q
State the function of a LDR.
A
To alter its resistance in response to the light intensity in the room.
21
Q
Define closed circuit.
A
A circuit where all wires are correctly connected and all switches are closed to create complete loops for current to flow through.
22
Q
Define open circuit.
A
A circuit where either wires are not correctly connected or switches are open so that no current can flow.
23
Q
Define electrical conductor.
A
A material that allows an electrical current to flow through it.
24
Q
Define electrical insulator.
A
A material that does not allow an electrical current to flow through it.
25
If a circuit is closed, explain how electrical charges can be made to flow.
By including a source of potential difference such as a cell or battery.
26
Name the charged subatomic particles that can flow in metals.
Electrons
27
Define electrical current in terms of charge.
Whether or not charges are flowing.
28
Define the size of an electrical current in terms of electrical charge.
The rate of flow of electrical charge
29
In terms of mathematics, define rate.
Divide by time (÷ t).
30
In words, state the equation that links charge flow, current and time.
charge flow = current × time
31
In symbols, state the equation that links charge flow, current and time.
Q = I × t
32
State the standard units for charge.
Coulombs (C)
33
State the standard units for current.
Amperes or amps (A)
34
State the standard units for time.
Seconds (s)
35
Describe the current throughout a closed loop within a circuit.
It has the same value everywhere in the circuit.
36
In the circuit diagram, compare the current at X with the current at Y.
They are the same.
37
Name the two variables that the current flowing through a component depends on.
Potential difference across the component and resistance of the component
38
If the potential difference across a component with fixed resistance is increased, describe the effect on the current.
The current increases.
39
If the resistance of a component is increased with a constant potential difference across it, describe the effect on the current.
The current decreases.
40
In words, state the equation that links potential difference, current and resistance.
potential difference = current × resistance
41
In symbols, state the equation that links potential difference, current and resistance.
V = I × R
42
State the standard units for potential difference.
Volts (V)
43
State the standard units for resistance.
Ohms (Ω)
44
To find the resistance of a component, identify the two variables that need to be measured experimentally.
Potential difference across the component and current flowing through it
45
When investigating how the length of a wire affects the resistance of the wire, name the independent variable.
Length of the wire
46
When investigating how the length of a wire affects the resistance of the wire, name the dependent variable.
Resistance of the wire
47
When investigating how the length of a wire affects the resistance of the wire, name three variables that need to be controlled.
Temperature of the wire, thickness of the wire and material the wire is made of
48
As the length of a wire is increased, describe the effect on the resistance of the wire.
The resistance should increase.
49
When measuring the resistance of a piece of wire, it is hard to attach the crocodile clips to exactly 0 cm. Identify the type of error this causes.
Zero error, a systematic error
50
When measuring the resistance of a piece of wire, explain why the potential difference should be kept small.
So there is a small current and the wire does not heat up as much.
51
A student wants to investigate the effect of the length of a piece of wire on its resistance. Outline a method to do this. Ensure the method would lead to valid results.
Connect two crocodile clips 10 cm apart on the piece of wire.
In series to the wire, connect a power source and an ammeter.
In parallel to the wire, connect a voltmeter.
Turn on the power source and measure the current and potential difference, then turn the power source off.
Reattach the crocodile clips 20 cm apart and repeat.
Calculate the resistance by dividing the potential difference by the current.
52
If two resistors are connected in series, state what this means in terms of loops.
They are connected in the same loop.
53
If two resistors are connected in parallel, state what this means in terms of loops.
They are connected in different loops.
54
If two resistors are connected in series, explain how the total resistance is calculated.
The total resistance increases as it is the sum of the two resistances.
55
A student wants to investigate the effect on the total resistance of placing two resistors in series compared to placing them in parallel. Outline a method to do this. Ensure the method would lead to valid results.
Connect the two resistors in series.
In series with the resistors, connect a power source and an ammeter.
In parallel, connect a voltmeter arcoss both resistors.
Turn on the power source and measure the current and potential difference, then turn the power source off.
Calculate the resistance by dividing the potential difference by the current.
Repeat with the resistors in parallel, but keep the voltmeter across both resistors and the ammeter measuring the current through the power source.
56
Name the only component whose resistance stays constant with increasing current.
Ohmic conductor (resistor)
57
The diagram shows an I-V curve. Name the component that would produce this curve.
Ohmic conductor (resistor)
58
The diagram shows the I-V curve for an ohmic conductor (resistor). Describe the graph in terms of the resistance of the component as potential difference increases.
The resistance stays the same as the potential difference increases.
59
Describe the relationship between potential difference and current for an ohmic conductor (resistor).
Current is directly proportional to potential difference.
60
Name four components which do not have fixed resistance when the current through them increases.
Lamps, diodes, thermistors and LDRs
61
The diagram shows an I-V curve. Name the component that would produce this curve.
Filament lamp
62
The diagram shows the I-V curve for a filament lamp. Describe the graph in terms of the resistance of the component as potential difference increases.
The resistance increases as the potential difference increases.
63
Explain why the resistance of a filament lamp increases with current.
The increased current increases the temperature.
64
The diagram shows an I-V curve. Name the component that would produce this curve.
Diode
65
The diagram shows the I-V curve for a diode. Describe the graph in terms of resistance of the component if the potential difference is in the reverse direction.
The resistance of the diode is very high in the reverse direction.
66
In a thermistor, describe how the resistance varies with temperature.
As the temperature increases, the resistance decreases.
67
Give a use of thermistors.
Electronic temperature sensors such as thermostats
68
In a LDR, describe how the resistance varies with light intensity.
As the light intensity increases, the resistance decreases.
69
Give a use of LDRs.
Electronic light sensors such as switching lights on when it gets dark
70
A circuit has a lamp, power supply and variable resistor. State two ways to increase the potential difference across the lamp.
Increase the potential difference of the power source (by adding more cells or using a power pack).
Decrease the resistance of the variable resistor.
71
When establishing the I-V curve of a component, name the independent variable.
Potential difference across the component
72
When establishing the I-V curve of a component, name the dependent variable.
Current flowing through the component
73
A student wants to establish the I-V curve of a filament bulb. Outline a method to do this. Ensure the method would lead to valid results.
Connect a filament bulb in series with a power pack and an ammeter.
Connect a voltmeter in parallel with the filament bulb.
Turn on the power pack at the lowest setting and measure the current and potential difference.
Turn up the power pack and repeat the two measurements.
Plot the measured potential difference (on the x-axis) against the measured current (on the y-axis).
74
Name the two main ways in which components can be joined together in a circuit.
In series and in parallel
75
Two components in a circuit are joined together in the same loop. Name the way in which they have been connected.
In series
76
Two components in a circuit are joined together in different loops. Name the way in which they have been connected.
In parallel
77
Describe the current through different components connected in series.
The current is the same through each component.
78
In the circuit diagram, describe the relationship between the potential difference in X and Y.
X + Y = 12 V
79
Describe the potential difference across different components when they are connected in series.
The total potential difference is shared between the components (but not necessarily equally).
80
Describe the total resistance across different components when they are connected in series.
The total resistance is the sum of individual resistances.
81
In words, state the equation for the total resistance of two resistors connected in series.
total resistance = resistance of resistor 1 + resistance of resistor 2
82
In symbols, state the equation for the total resistance of two resistors connected in series.
Rₜ = R₁ + R₂
83
Describe the current through different components connected in parallel.
The current through each component adds up to give the total current.
84
Describe what happens to the reading on the ammeter when the switch at the bottom is closed.
Nothing happens to the reading because the resistor and the bulb are in independent, parallel loops.
85
Describe the potential difference across different components when they are connected in parallel.
Each component gets the same potential difference (it is not shared).
