Topic 9 - Electricity and Circuits COMPLETE PK Flashcards
1
Q
1 What word describes materials that electricity will pass through?
A
conductors
2
Q
2 What word describes materials that electricity cannot pass through?
A
insulators
3
Q
3 What components do you need to make a circuit that would make a small torch bulb light up?
A
battery, connecting wires, lamp; switch is optional
4
Q
4 What are the two terminals of an electric cell labelled as?
A
plus and minus
5
Q
5 In an electric circuit with a battery, which of these materials will conduct: copper, wood, salty water?
A
copper and salty water
6
Q
6 Which of these materials are insulators: plastic, metal, air?
A
plastic and air
7
Q
7 What component is used to measure current?
A
ammeter
8
Q
8 What name is given to the negatively charged subatomic particles that cause an electric current?
A
electrons
9
Q
9 Is mains voltage about 15 times, 150 times or 1500 times bigger than the voltage from a battery?
A
about 150 times
10
Q
10 If you connect some cells together in series, what is formed?
A
a battery
11
Q
11 What is the name of a circuit with one path around it and no branches?
A
a series circuit
12
Q
12 What is the name given to a circuit with components in different branches?
A
a parallel circuit
13
Q
13 What is the circuit symbol for a lamp?
A
circle with a cross in it
14
Q
14 What is the circuit symbol for a cell?
A
two vertical lines, one longer than the other
15
Q
15 How can you tell which is the negative terminal of a cell from the circuit symbol?
A
It is the shorter line.
16
Q
16 What is the difference between conventional current and the flow of electrons?
A
Electrons flow from the negative terminal of a cell to the positive terminal, conventional current flows the other way.
17
Q
17 What unit is current measured in?
A
amps/amperes
18
Q
18 What is another term for potential difference?
A
voltage
19
Q
19 Which component is used to measure electric current?
A
an ammeter
20
Q
20 What are the units for current?
A
amps or amperes
21
Q
21 What two conditions are needed to give a current in a circuit?
A
closed circuit and potential difference
22
Q
22 Is an ammeter connected in parallel or in series with a component?
A
series
23
Q
23 A series circuit has two lamps. When the current through one lamp is 2A, what is the current through the other lamp?
A
2A
24
Q
24 A parallel circuit has two lamps in parallel. When the current through each lamp is 2A, what is the current from the battery?
A
4A
25
25 Which component is used to measure potential difference?
a voltmeter
26
26 What are the units for potential difference?
volts
27
27 Current can be described as the rate of flow of charge. In a metal, what are the charged particles that flow?
electrons
28
28 In a circuit, energy is transferred to a charge. Where is this energy transferred from?
cell/battery/power supply
29
29 What is an electric current?
a flow of charge
30
30 State the unit and the symbol for current.
amp/ampere, A
31
31 State the unit and the symbol for charge.
coulomb, C
32
32 Write down the equation relating the total charge that flows to current and time.
Q = I x t
33
33 State the unit and the symbol for potential difference.
volt, V
34
34 How many volts is one joule per coulomb?
1V
35
35 Write down the equation relating the energy transferred in a circuit to the potential difference.
E = Q x V
36
36 Describe the potential difference between two points in terms of energy transferred.
It is the energy transferred when 1 coulomb of charge moves from one point to the other.
37
37 State the unit for electrical resistance.
ohm
38
38 Write down the equation that is used to work out electrical resistance.
R = V / I
39
39 What unit is used to measure resistance?
ohms
40
40 What is the symbol for a resistor?
a rectangle
41
41 What is the symbol for a variable resistor?
a rectangle with an arrow through it
42
42 What equation connects potential difference, current and resistance?
V = I x R
43
43 A circuit contains a resistor. If another resistor is added in series with the first, does the total resistance in the circuit increase, decrease or stay the same?
increase
44
44 A circuit contains a resistor. If another resistor is added in parallel with the first, does the total resistance in the circuit increase, decrease or stay the same?
decrease
45
45 When resistors are connected in series, how can you calculate the total resistance?
add the resistances together
46
46 When the potential difference across a fixed resistor is doubled, what happens to the current?
the current doubles
47
47 What happens to the resistance of a light-dependent resistor LDR when light intensity increases?
It decreases
48
48 What happens to the resistance of a thermistor when the temperature increases?
it decreases
49
49 What is the name of a resistor that can be changed by adjusting a dial?
a variable resistor
50
50 Which component could be used to change the current in a circuit when the temperature changes?
a thermistor
51
51 Which component could be used to change the current in a circuit when the light intensity changes?
a light-dependent resistor
52
52 What does a diode do?
conducts electricity in only one direction
53
53 What happens to the resistance of a filament lamp when the potential difference is increased?
it increases
54
54 What happens to the resistance of a thermistor when the temperature rises?
it decreases
55
55 What happens to the resistance of a light-dependent resistor when the light intensity increases?
it decreases
56
56 What does the graph of current against potential difference look like for a fixed resistor?
straight line through the origin/directly proportional relationship
57
57 When an electric current passes through a high-resistance wire, what happens to the wire?
it becomes hot
58
58 How can resistance in the wires in circuits be reduced?
cool the wire / use low-resistance wire / make the wire thicker / make the wires as short as possible
59
59 Give an example of an appliance that uses the heating effect of a current.
e.g. kettle
60
60 Give an example of a disadvantage that can result from overheating by an electric current.
e.g. fire, damage to the appliance/wires
61
61 If the new connecting wires in a house have a lower resistance than the old ones, what effect will this have on daily electricity use?
it will be less
62
62 When electrons move through a lattice of positive ions, what happens to cause electrical resistance?
collisions
63
63 When a resistor heats up, what happens to the positive ions to increase resistance?
they vibrate more
64
64 What is the equation that connects energy transferred to current, potential difference and time?
E = I x V x t, energy transferred = current x potential difference x time
65
65 H Apart from using lower resistance wires and without changing any components, state one way the resistance in a circuit can be reduced.
thicker wires, cooling
66
66 H State a second way the resistance in circuits can be reduced.
low resistance materials, thicker wires, or cooling
67
67 What is the unit for measuring power?
watts
68
68 Power is the transfer of what each second?
energy
69
69 Name the unit and give the symbol for power.
watt, W
70
70 Which is more powerful: kettle A, which boils a mug of water in 1 minute, or kettle B, which boils a mug of water in 2 minutes, or do they both have the same power?
A
71
71 Write down an equation that links power to energy transferred, E.
or in words
72
72 Which uses more power: A a 12 V 20 W lamp, or B a 240 V 9 W lamp or do they both use the same power?
A
73
73 Write down an equation that links power to current and potential difference.
P = I x V or in words
74
75 What is the mains voltage in the UK?
230 V
75
76 What is the frequency of the a.c. mains voltage in the UK?
50 Hz
76
77 What type of energy store does a battery have?
chemical
77
78 At some time after energy is transferred to an electric toothbrush, in what energy store does the energy end up?
in the thermal store of the surroundings
78
79 What do the letters d.c. mean?
direct current
79
80 Describe the way the electrons move in d.c.
in one continuous direction
80
81 What do the letters a.c. mean?
alternating current
81
82 Describe the way the electrons move in a.c.
keep reversing direction
82
83 What are the names of two of the wires in a plug?
two of: live, neutral, earth
83
84 What is the name of one electrical safety feature found in our homes apart from the earth wire of a plug?
Circuit breaker or fuse
84
What component of an electrical circuit does this symbol represent?
Open switch
85
What component of an electrical circuit does this symbol represent?
Closed switch
86
What component of an electrical circuit does this symbol represent?
Lamp
87
What component of an electrical circuit does this symbol represent?
Voltmeter
88
What component of an electrical circuit does this symbol represent?
Ammeter
89
What component of an electrical circuit does this symbol represent?
Resistor
90
What component of an electrical circuit does this symbol represent?
LDR
91
What component of an electrical circuit does this symbol represent?
Thermistor
92
What component of an electrical circuit does this symbol represent?
Variable Resistor
93
What component of an electrical circuit does this symbol represent?
Diode
94
What component of an electrical circuit does this symbol represent?
LED
95
What component of an electrical circuit does this symbol represent?
Fuse
96
What component of an electrical circuit does this symbol represent?
Cell
97
What component of an electrical circuit does this symbol represent?
Battery
98
Is this an example of a series circuit or a parallel circuit?
Series
99
Is this an example of a series circuit or a parallel circuit?
Parallel
100
True/False: You can run your finger all the way through a series circuit from the battery to all the components
True
101
True/False: You can run your finger all the way through a parallel circuit from the battery to all the components
False
102
In a series circuit, the voltmeter has to be in series/in parallel around the component
in parallel
103
What is charge?
The value of electricity flowing through a circuit
104
What is current?
The flow of electrons
105
What is potential difference?
What pushes the current around
106
What is resistance?
Anything that slows down the current
107
Energy =
charge x potential difference
108
What is charge measured in?
coulombs
109
Charge =
Current x time
110
In a series circuit, electrons all move in the same/different paths
The same
111
The current in a series circuit changes/stays the same
Stays the same
112
Current in a parallel circuit is...
split across the branches
113
What is potential difference measured by?
A voltmeter
114
In a series circuit, potentiall difference is split/the same across components
Split
115
In a parallel circuit, potentiall difference is split/the same across components
The same
116
With resistors in series, the total resistance is...
The resistors added together
117
With resistors in parallel, the total resistance is...
1/resistance1 + 1/resistance2 etc
118
Current in a series circuit is...
The same wherever you look at it
119
What must you do with different potential differences in a series circuit to get the total potential difference?
Add them together
120
What must you do with different resistances in a series circuit to get the total resistance?
Add them together
121
In a parallel circuit, the current on each branch is equal to...
the total current
122
In a parallel circuit, the potential difference in each branch is...
The same
123
Potential difference =
Current x resistance
124
In a current/potential difference graph, what is the relationship between a resistor and a constant temperature?
They are directly proportional
125
What does this current/potential difference graph represent?
A filament bulb
126
What does this current/potential difference graph represent?
A diode
127
Diodes let current flow in multiple directions/only let current flow in one direction
Only let current flow in one direction
128
What is a thermistor used in?
Things like central heating
129
Thermistors only let _______ flow at certain temperatures
current
130
What does this graph show about the flow of current from thermistors?
Only lets current flow at certain temperatures - the graph is more steep at high temperatures. As the temperature changes, the resistance changes
131
What does LDR stand for?
Light Dependant Resistor
132
What are LDRs used in?
Street lights and security lights
133
What does this graph show about how resistance flowing through a circuit is affected by light?
Resistance flowing through the circuit changes with the amount of light
134
Energy =
Current x potential difference x time
135
Power =
_energy transferred_
time
or
potential difference x current
or
current2 x resistance
136
What is resistance measured in?
Ohms
137
Mains electricity in the UK is \_\_\_V and \_\_Hz
250V and 50Hz
138
What goes through the fuse?
A very small bit of wire
139
What happens to the wire in the fuse if too much current goes through it?
It will melt
140
Why does the wire in the fuse melt if too much current goes through?
This protects the wiring and the appliance if something goes wrong
141
Name the 3 wires in a plug
Live wire, earth wire and neutral wire
142
Which wire, neutral, earth or live is a safety feature of plugs?
Earth
143
What holds wires down in a plug?
Pins
144
True/False, the cable grip in a wire is a safety feature
True
145
What does the cable grip do?
Makes sure the wire doesn't go anywhere
146
The cable for a plug is ______ incased in plastic
double
147
Why are plugs cased in plasted?
Safety reasons
148
What does AC stand for?
Alternating Current
149
What does DC stand for?
Direct current
150
Alternating Current comes from...
Mains electricity
151
Direct current comes from...
Batteries
152
What is alternating current?
Current that changes - it goes one way or the other way
153
What is direct current?
Current that just goes one way
154
What is static electricity?
An object that isn't normally charged becoming charged
155
What causes static electricity?
Two insulators rubbing together
156
What causes two insulators to rub together?
The movement of electrons from one thing to another
157
What happens when static electricity charges reset?
You get a shock
158
How do static electricity charges reset?
When you touch something metal
159
Two charged objects coming together will _____ each other
Repel
160
A charged object and an oppositely charged object will _______ each other
attract
