11 mark
This is the circuit symbol for which component?
A fuse
A buzzer
A transistor
A relay
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4.3 Electric Circuits & Electrical Safety
21 mark
Which of the following circuit symbols is for a thermistor?
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31 mark
Which of the circuit diagrams above shows a fuse which has been correctly connected?
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41 mark
The diagram shows two resistors connected in parallel.
The total resistance of this combination will be:
The sum of 2.0 Ω and 4.0 Ω
Greater than 4.0 Ω
Between 2.0 Ω and 4.0 Ω
Less than 2.0 Ω
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51 mark
Extended
Which diagram shows the correct symbol for a diode, and the correct direction of current moving through it?
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11 mark
A homeowner buys a security light that switches on automatically when it gets dark.
The security light contains the circuit, shown below.
When it gets dark, what happens to the resistance of the LDR, and what happens to the potential difference across the LDR?
|
Resistance of LDR |
p.d. across LDR |
|
|
A |
increases |
increases |
|
B |
decreases |
increases |
|
C |
increases |
decreases |
|
D |
decreases |
decreases |
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21 mark
A student sets up four circuits containing diodes. These circuits are shown below.
Which of the circuits will produce a rectified current through the bulb?
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31 mark
Two resistors are connected in parallel.
What is the combined resistance of the combination?
20 Ω
4.8 Ω
0.21 Ω
1.5 Ω
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41 mark
Two resistors are connected in parallel.
The current through the top resistor is 2.0 A.
What is the reading on the ammeter?
6.0 A
2.0 A
4.0 A
3.5 A
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51 mark
A 10 Ω and a 30 Ω resistor are connected in series, as shown in the diagram below, making a potential divider circuit.
What would be the reading on the voltmeter?
2.0 V
6.0 V
4.0 V
8.0 V
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61 mark
Which of the following statements about the current in ammeters X, Y and Z is correct?
The current through X equals the current through Y + the current through Z.
The current through X is equal to the current through Z.
The current through X is equal to the current through Y.
The current through Y is greater than the current through Z.
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71 mark
All the light bulbs in the diagrams above are identical. Each one is rated as
‘10 W 230 V’.
In which of the diagrams are all the bulbs working at their normal brightness?
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81 mark
A student connects together some identical resistors in three different combinations, as shown in the diagram.
Which of the answers below shows the correct order of the combinations from the lowest resistance to the highest?
P → Q → R
Q → P → R
Q → R → P
P → R → Q
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91 mark
A teacher writes a set of notes about two non-identical bulbs which are connected in parallel.
He makes one mistake. Which of the statements below is incorrect?
They have the same current flowing through them.
They have the same potential difference across them.
They can be switched on and off individually.
If one bulb blows, the other will continue to work.
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101 mark
A person wants to install a circuit breaker to protect themselves and their lawnmower from too much current.
Under normal operating conditions, the lawnmower carries 4 A of current.
The manufacturer provides the graph below with the circuit breaker.
What will happen when the current is 4 A, and what will happen if the current rises to 14 A?
|
4 A |
14 A |
|
|
A |
circuit does not break |
circuit does not break |
|
B |
circuit does not break |
circuit breaks quickly |
|
C |
circuit breaks quickly |
circuit does not break |
|
D |
circuit breaks quickly |
circuit breaks quickly |
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11 mark
The plug for an electric lamp contains a 3 A fuse. The fuse’s job is to protect the lamp if too much current flows.
Where is the fuse positioned, and what happens when the fuse does its job?
|
Where is it positioned? |
What does it do? |
|
|
A |
live wire |
reduces the current to 3 A |
|
B |
neutral wire |
breaks the circuit |
|
C |
live wire |
breaks the circuit |
|
D |
neutral wire |
reduces the current to 3 A |
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21 mark
Which of the diagrams below shows a fuse which has been correctly connected to a circuit?
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31 mark
Both fuses and circuit breakers are devices which protect devices from high currents that could cause them to get too hot and catch fire.
The diagram shows two possible positions where a fuse or a circuit breaker could be positioned.
Which location would be suitable for a fuse, and which would be suitable for a circuit breaker?
|
fuse |
circuit breaker |
|
|
A |
P |
P |
|
B |
P |
Q |
|
C |
Q |
P |
|
D |
Q |
Q |
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41 mark
The diagram shows two bulbs, which have been connected in parallel. A fuse has been included in the circuit.
Each of the ammeters reads 1.2 A.
What fuse should be put in this circuit?
1.0 A
3.0 A
5.0 A
13.0 A
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51 mark
The fuse blows in a kettle, and the owner of the kettle, Brooke Bond decides to replace the fuse. The fuse he takes out has 13 A written on it.
Brooke does not have any fuses in the cupboard with 13 A written on them, so he replaces it with a fuse that has 3 A written on it.
He then switches the kettle on to make a nice cup of tea. What happens?
The kettle explodes in a shower of sparks and molten plastic.
The fuse does not blow, and the kettle operates normally.
The fuse blows and the kettle remains undamaged.
The fuse does not blow, but the kettle does not work.
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61 mark
The diagram shows a toaster that has been wired up.
Three fuses have been connected to the toaster, but only one or two have been connected correctly.
Which of the fuses has been positioned correctly?
Fuse X and fuse Y
Fuse X only
Fuse Z only
Fuse X and fuse Z
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71 mark
An oven is wired into somebody’s kitchen. The oven is protected by a fuse, and functions normally, but the owner notices that the wires that connect the oven to the mains electricity supply get quite hot.
What could be done to reduce the temperature of the wires?
Add a circuit breaker to the circuit.
Put thicker insulation on the wires.
Replace the wires with thicker diameter wires.
Replace the wires with thinner diameter wires.
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81 mark
The diagram shows two resistors connected in series with a battery.
What is the current through the battery?
1.5 A
150 A
0.67 A
15 A
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91 mark
A book shop owner sets up the circuit below, but they find that the lamp is too dim.
What change can be made to the circuit to increase the brightness of the bulb?
Putting another resistor in parallel with the battery.
Putting a resistor in parallel with the bulb.
Putting another resistor in series with the resistor.
Putting another resistor in parallel with the resistor.
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101 mark
A student sets up the circuit below, it contains four fuses and four bulbs.
She finds that none of the bulbs are lit, but only one of the fuses has blown.
Which fuse has blown?
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