Separate Physics - P2 Electricity Flashcards
1
Q
What is the circuit symbol for an open switch?
A
2
Q
What is the circuit symbol for a closed switch?
A
3
Q
What is the circuit symbol for a cell?
A
4
Q
What is the circuit symbol for a battery?
A
5
Q
What is the circuit symbol for a diode?
A
6
Q
What is the circuit symbol for a resistor?
A
7
Q
What is the circuit symbol for a variable resistor?
A
8
Q
What is the circuit symbol for an LED?
A
9
Q
What is the circuit symbol for a lamp?
A
10
Q
What is the circuit symbol for a fuse?
A
11
Q
What is the circuit symbol for a voltmeter?
A
12
Q
What is the circuit symbol for an ammeter?
A
13
Q
What is the circuit symbol for a thermistor?
A
14
Q
What is the circuit symbol for an LDR?
A
15
Q
What is current?
A
The rate of flow of charge
16
Q
What equation links charge flow, current and time?
A
Charge flow = current x time
Q = I t
17
Q
Describe the IV graph for a resistor at constant temperature.
A
- Current is directly proportional to potential difference.
- Resistance is constant.
18
Q
What type of circuit is shown in the image?
A
Series circuit
19
Q
Explain the shape of the IV graph for a diode.
A
- Current only flows in one direction through a diode.
- There is high resistance in the opposite direction meaning current doesn’t flow.
20
Q
What equation links potential difference, current and resistance?
A
Potential difference = current x resistance
V = I R
21
Q
What type of circuit is shown in the image?
A
Parallel circuit
22
Q
Draw an I-V graph for a filament lamp.
A
23
Q
For a given potential difference, what happens to the current when the resistance increases?
A
The current decreases.
24
Q
Explain the shape of the IV graph for a filament lamp.
A
As the current increases the temperature of the filament lamp increases (so the resistance increases) meaning less current can flow per unit potential difference.
25
Draw an I-V graph for an ohmic resistor (e.g. a resistor at a constant temperature).
26
Draw an I-V graph for a diode.
27
What happens to the resistance of a thermistor as temperature increases?
Resistance decreases
28
What happens to the resistance of an LDR as light increases?
Resistance decreases
29
What’s the difference between direct current and alternating current?
* Direct current flows in only one direction.
* Alternating current constantly changes direction.
30
What is the rule for current in a series circuit?
Current is **_the same_** everywhere in the circuit
31
Name the electrical component used in thermostats.
Thermistor
32
Where are LDRs commonly found?
LDRs are used as automatic night lights / burglar detectors (in bright light the resistance is low)
33
What is the National Grid?
A system of cables and transformers
34
What is the rule for potential difference in a series circuit?
Potential difference is **_shared_** between components.
35
Where should you place an ammeter to measure current through a component?
The ammeter should be placed in series with the component.
36
What is the rule for potential difference in a parallel circuit?
It is the same in each branch.
37
Where should you place a voltmeter to measure potential difference across a component?
The voltmeter should be placed parallel to the component.
38
What type of electricity supply is a battery?
Direct current (DC)
39
What is the total resistance of the three resistors in series?
25 Ω
40
What is the rule for current in a parallel circuit?
Current is **_shared_** between the branches.
41
What type of electricity supply is mains electricity?
Alternating current (AC)
42
Name the equipment used to measure potential difference.
Voltmeter
43
What is the frequency of mains electricity?
50 Hz
44
Name the three wires in a three-core cable and say what colour they are.
* Live wire (brown)
* Neutral wire (blue)
* Earth wire (green / yellow striped)
45
What is the function of the neutral wire (blue)
Completes the circuit carrying current away (0 V)
46
What equation links power, current and resistance?
Power = current2 x resistance
P = I2 R
47
What is the potential difference of mains electricity?
230 V
48
What is the function of the live wire (brown)?
Provides the alternating potential difference (230V)
49
What is the function of the Earth wire (green / yellow)?
Acts as a safety device, stopping the appliance casing from becoming live (0 V)
50
What equations links power, current and potential difference?
Power = current x potential difference
P = I V
51
What two things determine how much energy is transferred by an electrical appliance.
* How long the appliance is on for
* The power rating of the appliance
52
What equation links energy transferred, charge flow and potential difference?
Energy transferred = charge flow x potential difference
E = Q V
53
In a parallel circuit, what happens to the total resistance when you add a resistor?
The total resistance decreases.
54
Describe how electricity is transmitted across the National Grid to make it as efficient as possible.
* High potential difference
* Low current
* Which decreases energy lost by heating the wires/surrounding
55
What equation links energy transferred, power and time?
Energy transferred = power x time
E = P t
56
How are step-down transformers used within the National Grid?
Step-down transformers bring the 400,000 V of the National Grid down to 230 V for use in the home.
57
Name the equipment used to measure current.
Ammeter
58
How are step-up transformers used within the National Grid?
Step-up transformers increase the potential difference of the National Grid to 400,000 V
59
Sketch a graph to show resistance against length of wire.
60
Sketch a graph to show how light intensity affects resistance in an LDR.
61
Sketch a graph to show how temperature affects resistance in a thermistor.
62
Sketch a graph to show how the number of resistors affects resistance in a series circuit.
63
Describe how you would use the equipment to investigate how the length of wire affects resistance.
* Connect crocodile clips across 10 cm of wire and connect to a power supply.
* Measure current using ammeter
* Measure potential difference using voltmeter
* Calculate resistance using the equation R=V/I
* Repeat for different lengths of wire (20 cm, 30 cm, 40 cm, 50 cm 60 cm)
64
Describe how you would use the equipment to investigate the relationship between current and potential difference across a resistor.
* Place a variable resistor and ammeter in series with a resistor.
* Place a voltmeter parallel to the resistor.
* Measure current using an ammeter.
* Measure potential difference using a voltmeter.
* Use the variable resistor to adjust current.
* Take new readings for current and potential difference.
* Repeat until you have 5 sets of readings and plot a graph of current (I) against potential difference (V).
65
Describe how to use the following equipment to investigate how adding resistors in series affects total resistance.
1. Take reading off voltmeter for potential difference
2. Take reading off ammeter for current
3. Calculate resistance using the equation R=V/I
4. Add a resistor in series with the first one (in the same loop) and repeat steps 1-3.
5. Repeat this with up to 5 resistors.
66
Describe how to use the following equipment to investigate how adding resistors in parallel affects total resistance.
1. Take reading off voltmeter for potential difference
2. Take reading off ammeter for current
3. Calculate resistance using the equation R=V/I
4. Add a resistor parallel to the first one (in a separate branch) and repeat steps 1-3.
5. Repeat this with up to 5 resistors.
67
**Separate Q.** When two insulating materials are rubbed together, what charge will the material that gains electrons have?
Negative
68
**Separate Q.** When certain insulating materials are rubbed together, what will be scraped off one and transferred onto the other?
Electrons
69
**Separate Q.** What do like charges do?
Repel
70
**Separate Q.** Name the force that causes a build up of static charge.
Friction
71
**Separate Q.** When two insulating materials are rubbed together, what charge will the material that loses electrons have?
Positive
72
**Separate Q.** Name the force exerted between charged objects.
Electrostatic
73
**Separate Q.** What do opposite charges do?
Attract
74
**Separate Q.** Explain how the build up of electric charge can cause a spark.
* As electric charge builds on an object, the potential difference between the object and Earth increases.
* A high potential difference causes a strong electric field between the object and Earth.
* Electrons are stripped from the air between the object and Earth – the air is ionised.
* The air is now much more conductive so current can flow.
* If the potential difference is large enough, electrons will jump from the object towards Earth (the spark).
75
**Separate Q.** Describe the relationship between the strength of an electric field and the distance from the charge object.
The closer to the object, the stronger the electric field. The further away from the object, the weaker the electric field.
76
**Separate Q.** In what direction do electric field lines always point?
From positive to negative
77
**Separate Q.** At what angle from the surface of an object should electric field lines be drawn?
Right angles / 90o
78
**Separate Q.** Charged objects interact with each other without touching. What ‘type’ of force does this describe?
Non-contact force
79
**Separate Q.** Draw the field lines for a positively charged object.
80
**Separate Q.** Draw the field lines for a negatively charged object.
81
**Separate Q.** What happens when two electrically charged objects are brought close together?
They exert a force on each other
82
**Separate Q.** What type of field is created around a charged object?
Electric field
