CIE iGCSE Co-Ordinated Science P4.4 Electrical safety Exam Style Questions Paper 1
Question
A student connects the circuit shown.
When the switch is closed, the fuse blows and stops the current.
What is a possible reason for this?
A. The current rating of the fuse is too high.
B. The current is too large.
C. The lamp is too dim.
D. The voltage is too small.
▶️Answer/Explanation
Answer: B
Explanation: If the current in the circuit exceeds the fuse’s rating, the fuse will blow to protect the circuit. This indicates that the current is too large.
Question
A hairdryer is protected by a 10 A fuse. What is the purpose of the fuse?
A. It decreases the current in the hairdryer to 10 A when the current is more than 10 A.
B. It increases the current in the hairdryer to 10 A when the current is less than 10 A.
C. It maintains a constant temperature in the hairdryer.
D. It melts when the current in the hairdryer is greater than 10 A.
▶️Answer/Explanation
Answer: D. It melts when the current in the hairdryer is greater than 10 A.
Explanation: A fuse is a safety device that melts and breaks the circuit if the current exceeds a certain value (in this case, 10 A), preventing damage to the appliance or wiring.
Question
An electric kettle, washing machine and cooker are all switched on and connected through an extension cable into a single mains socket.
What is the electrical hazard of this arrangement?
A) The cooker overheats.
B) The extension cable overheats.
C) The kettle overheats.
D) The washing machine overheats.
▶️Answer/Explanation
Answer: B) The extension cable overheats.
Explanation: Connecting multiple high-power appliances to a single extension cable can cause the cable to overheat due to excessive current flow, posing a fire hazard.
Question
The table shows the usual current in each of four household appliances and the fuse used to protect each of them. The only fuses available are rated at 3 A, 5 A or 13 A. Which row shows an appliance that has been fitted with the most appropriate of the fuses available?
| Appliance | Current / A | Fuse rating / A | |
|---|---|---|---|
| A | Hairdryer | 5.5 | 5 |
| B | Kettle | 7.5 | 13 |
| C | Lawnmower | 5.0 | 3 |
| D | Slow cooker | 1.0 | 5 |
▶️Answer/Explanation
Answer: B Kettle
Explanation: The fuse rating should be slightly higher than the usual current to allow for small surges without blowing the fuse. For the kettle, a 13 A fuse is appropriate as it is higher than the usual current of 7.5 A.
Question
The diagram shows a circuit containing an electric heater, a motor and a fuse.
The current in the heater is 6.0A and the current in the motor is 2.0A.
What is an appropriate rating for the fuse?
A 2A B 4A C 6A D 10A
▶️Answer/Explanation
Ans :A
Question
A device that is designed to protect a circuit contains a thin wire. When there is a large current
in the circuit, the thin wire melts and cuts off the supply.
What is the device?
(A) fuse
(B) lamp
(C) resistor
(D) thermistor
▶️Answer/Explanation
Ans: A
Question
The maximum current in a food mixer during normal use is 3.1 A.
What is the most suitable rating for a fuse used to protect the mixer?
(A) 1A
(B) 3A
(C) 5A
(D) 8A
▶️Answer/Explanation
Ans: C
Question
The current in an electric heater during normal use is 11A.
What is an appropriate rating for a fuse to protect the heater?
(A) 3A
(B) 10A
(C) 13A
(D) 36A
▶️Answer/Explanation
Ans : C
Question
The current in an electric heater is 10A when in normal use. The heater circuit contains a fuse.
What is the purpose of the fuse and what is a suitable rating for the fuse?
▶️Answer/Explanation
Ans : D
Question
Fuses are used in domestic electric circuits.
Which statement about fuses is correct?
(A) A fuse is connected in the live wire.
(B) A fuse is connected in the neutral wire.
(C) A 3.0A fuse produces a current of exactly 3.0A in the circuit.
(D) A 3.0A fuse produces a minimum current of 3.0A in the circuit.
▶️Answer/Explanation
Ans : A
Question
What is the purpose of a fuse in an electric circuit?
(A) to make the circuit more efficient
(B) to protect the circuit from damage by a large current
(C) to provide a constant current in the circuit
(D) to provide a constant potential difference (p.d.) across the circuit
▶️Answer/Explanation
Ans: B
Question
The current in an electric kettle used to boil water is 9.0A.
What is the most appropriate rating of fuse to use with this kettle?
(A) 1A
(B) 3A
(C) 8A
(D) 13A
▶️Answer/Explanation
Ans : D
Question
The current in an electric heater is 6.0A when in normal use.
Four fuses with different ratings are available to protect the wire to the heater.
Which fuse is most suitable?
(A) 1A (B) 5A (C) 8A (D) 20A
▶Answer/Explanation
Ans : C
Question
The maximum current in an electric circuit is 10A.
What is the most appropriate rating of a fuse for this circuit?
(A) 5A (B) 9A (C) 13A (D) 25A
▶️Answer/Explanation
Ans: C
Question
An electric kettle is designed so that the usual current in its heater is 9.0 A. The owner of the kettle fits the plug with a fuse rated at 3 A. What happens when the kettle is filled with water and switched on?
A) The current in the circuit increases to greater than 9.0 A.
B) The fuse blows immediately and the kettle fails to operate.
C) The water reaches boiling point more quickly due to an increase in the voltage.
D) The water reaches boiling point more slowly due to a decrease in the current.
▶️Answer/Explanation
Answer: B) The fuse blows immediately and the kettle fails to operate.
Explanation: The fuse is rated at 3 A, which is lower than the usual current of 9.0 A. When the kettle is switched on, the current exceeds the fuse rating, causing the fuse to blow and the kettle to fail to operate.
Question
Fuses are used in domestic electric circuits. Which statement about fuses is correct?
A. A fuse is connected in the live wire.
B. A fuse is connected in the neutral wire.
C. A 3A fuse produces a current of exactly 3A in the circuit.
D. A 3A fuse produces a minimum current of 3A in the circuit.
▶️Answer/Explanation
Answer: A. A fuse is connected in the live wire.
Explanation: A fuse is connected in the live wire to protect the circuit. If the current exceeds the fuse’s rating, it will melt and break the circuit, preventing damage or fire.
Question
A fuse is a safety device for use in an electrical circuit. The current in the circuit becomes greater than the rated value for the fuse.
What happens?
A) The current decreases to zero.
B) The current decreases to the rated value for the fuse.
C) The thickness of the insulation around the wires increases.
D) The current is sent to the outer case of the appliance.
▶️Answer/Explanation
Answer: A
Explanation: A fuse is designed to break the circuit when the current exceeds its rated value. When this happens, the current decreases to zero, preventing damage to the circuit or appliance. Therefore, the correct answer is A.
Question
An electrical extension block has four sockets, a cable which can safely take a current of 6A and a plug. It is protected by a fuse rated at 5A.
The extension block is used with four appliances and the 5A fuse blows. The owner replaces the 5A fuse with a 13A fuse.
Why is the extension block now dangerous?
A The appliances may overheat before the fuse blows.
B The cable may overheat before the fuse blows.
C The sockets may burn out before the fuse blows.
D The 13A fuse may blow too soon.
▶️Answer/Explanation
Answer: B
Explanation: The cable is rated for 6A, so if a 13A fuse is used, the cable could overheat and cause a fire before the fuse blows.