Safety with electricity - Natural Science Grade 9 PDF Download
Section A: Multiple Choice
Choose the correct answer for each question. Write only the letter (A-D) of your answer.
Question 1
Which of the following is the safest action to take before repairing an electrical appliance at home?
A. Wear rubber gloves while the appliance is plugged in
B. Switch off the appliance and disconnect it from the power source
C. Use a metal screwdriver to open the appliance while it is on
D. Pour water on the appliance to cool it down first [2]
Question 2
What is the main purpose of an earth wire in a three-pin plug?
A. To carry current to the appliance during normal operation
B. To provide a safe path for current if there is a fault in the appliance
C. To increase the voltage supplied to the appliance
D. To make the plug fit tightly into the socket [2]
Question 3
Thabo notices that an electrical cord has exposed wires. What should he do?
A. Continue using the cord because it still works
B. Wrap the exposed section tightly with aluminium foil
C. Stop using the cord immediately and have it replaced or properly insulated
D. Touch the exposed wires to check if electricity is flowing [2]
Question 4
Why is it dangerous to use electrical appliances with wet hands?
A. Water is a good conductor of electricity and increases the risk of electric shock
B. Water makes the appliance work faster and may cause it to overheat
C. Wet hands can damage the appliance permanently
D. Water prevents electricity from flowing through the appliance [2]
Section B: True or False
State whether each of the following statements is TRUE or FALSE.
Question 1
A circuit breaker automatically cuts off the electricity supply when there is an overload or short circuit in the system. [1]
Question 2
It is safe to overload a single wall socket by plugging in multiple high-power appliances using an adapter. [1]
Question 3
Insulating materials such as rubber and plastic are used to cover electrical wires to prevent electric shock. [1]
Question 4
If someone receives an electric shock, you should immediately touch them with your bare hands to pull them away from the source. [1]
Section C: Match the Column
Match each item in Column A with the correct description in Column B. Write only the letter of the correct match next to the question number.
[4]
Section D: Fill in the Blanks
Complete the following sentences using the words from the word bank below. Use each word only once.
Word Bank: earthing, shock, electrocution, short circuit
Question 1
A ________ occurs when the live wire comes into direct contact with the neutral wire, causing a large current to flow suddenly. [1]
Question 2
________ is the process of connecting the metal casing of an appliance to the ground so that fault current flows safely into the earth. [1]
Question 3
An electric ________ occurs when current flows through a person's body, causing injury or even death. [1]
Question 4
________ refers to death caused by electric current passing through the body. [1]
Section E: Short Questions
Question 1
Explain why it is important to never fly a kite near overhead power lines. [2]
Question 2
Name two safety devices used in household electrical circuits and state the function of each. [4]
Question 3
Describe what you should do if you see someone being electrocuted. [3]
Question 4
Why should electrical appliances not be used in the bathroom or near water? [2]
Section F: Scenario Question
Nomsa is helping her mother in the kitchen. She notices that the toaster's power cord is frayed and some of the internal wires are visible. Her younger brother, Bongani, wants to use the toaster to make breakfast. Nomsa also sees that her mother has plugged the toaster, kettle, microwave, and a fan into a single four-way adapter connected to one wall socket.
Question 1
Identify two electrical safety hazards present in this scenario. [2]
Question 2
Explain why the frayed cord is a danger to anyone who uses the toaster. [2]
Question 3
What could happen if all four appliances are used at the same time from one socket, and why? [3]
Question 4
Suggest two safe actions Nomsa should take immediately to reduce the risk of electrical accidents. [2]
Section G: Long Question
Lerato's family has just moved into a new home. Her father is installing new electrical appliances and notices that some of the wall sockets only have two holes, while others have three. He is unsure whether to use two-pin or three-pin plugs for different appliances. Lerato recalls learning about electrical safety at school and decides to help her father understand the importance of earthing and the role of different safety devices.
Question 1
Explain the difference between a two-pin plug and a three-pin plug, and state which type is safer for high-power appliances such as a stove or geyser. [3]
Question 2
Describe how the earth wire in a three-pin plug protects users from electric shock if a fault occurs inside an appliance. [4]
Question 3
Lerato's father wants to know whether he should install a residual current device (RCD) in the home. Explain what an RCD is and why it is an important safety feature in modern homes. [4]
Question 4
Evaluate the risks of using an appliance with a damaged plug or faulty wiring, and recommend what should be done before using such an appliance. [4]
Grand Total: [60]
Answer Key
Well done for completing the worksheet! Remember to check your answers carefully and use this key to guide your learning. Try to understand why each answer is correct - this will help you remember important safety concepts. Always attempt all questions before checking your answers.
Section A - Question 1
Answer: B - Switch off the appliance and disconnect it from the power source.
This is the safest action because it ensures that no current is flowing through the appliance while you work on it, which prevents electric shock.
Section A - Question 2
Answer: B - To provide a safe path for current if there is a fault in the appliance.
The earth wire connects the metal casing of an appliance to the ground. If a live wire touches the casing, the earth wire carries the current safely into the earth, preventing electric shock to the user.
Section A - Question 3
Answer: C - Stop using the cord immediately and have it replaced or properly insulated.
Exposed wires can cause electric shock or short circuits. The cord must be repaired or replaced by a qualified person to ensure safety.
Section A - Question 4
Answer: A - Water is a good conductor of electricity and increases the risk of electric shock.
When your hands are wet, water can conduct electricity from the appliance into your body, causing a dangerous electric shock.
Section B - Question 1
TRUE
A circuit breaker is designed to detect overloads or short circuits and automatically switch off the power supply to protect the circuit and prevent fires or damage.
Section B - Question 2
FALSE
Corrected statement: It is not safe to overload a single wall socket by plugging in multiple high-power appliances using an adapter.
Overloading a socket can cause overheating, melting of wires, and even electrical fires because the socket and wiring are not designed to carry such high currents.
Section B - Question 3
TRUE
Insulating materials like rubber and plastic do not conduct electricity, so they are used to cover wires and prevent users from coming into contact with live conductors.
Section B - Question 4
FALSE
Corrected statement: If someone receives an electric shock, you should not touch them with your bare hands; instead, switch off the power source or use a non-conductive object to separate them from the source.
Touching the person directly can cause the current to flow through your body as well, putting you at risk of electric shock.
Section C - Match the Column
- 1 - A: A fuse contains a thin wire that melts when current exceeds a safe level, breaking the circuit and protecting appliances and users.
- 2 - B: An electrical insulator is a material like plastic, rubber, or wood that does not allow current to pass through, preventing shocks.
- 3 - C: Double insulation means the appliance has two separate layers of insulation, so it does not need an earth wire for safety.
- 4 - D: A residual current device (RCD) monitors the balance of current in live and neutral wires and cuts off power instantly if there is a leakage, protecting against electrocution.
Section D - Question 1
Answer: short circuit
A short circuit happens when live and neutral wires touch directly, creating a path of very low resistance that causes a sudden surge of current.
Section D - Question 2
Answer: earthing
Earthing provides a safe route for fault currents to flow into the ground, preventing the metal casing of an appliance from becoming live and dangerous.
Section D - Question 3
Answer: shock
An electric shock is caused when current passes through the body, which can lead to injury, burns, or even death depending on the current and duration.
Section D - Question 4
Answer: electrocution
Electrocution specifically means death resulting from electric shock, usually caused by high voltage or prolonged exposure to current.
Section E - Question 1
Model Answer:
Flying a kite near overhead power lines is dangerous because the kite or string can come into contact with the high-voltage wires, causing a powerful electric shock that can be fatal. Even if the kite does not touch the wires directly, electricity can arc through the air if the kite is close enough.
Mark breakdown: danger of contact [1], risk of fatal shock or arcing [1]
Section E - Question 2
Model Answer:
Two safety devices are the fuse and the circuit breaker. A fuse contains a thin wire that melts and breaks the circuit when the current is too high, protecting appliances and preventing fires. A circuit breaker is a switch that automatically trips to cut off the electricity supply when it detects an overload or short circuit, and it can be reset after the fault is fixed.
Mark breakdown: naming two devices [2], function of each device [2]
Section E - Question 3
Model Answer:
If you see someone being electrocuted, do not touch them directly with your hands. First, try to switch off the power source at the mains or socket. If this is not possible, use a non-conductive object such as a dry wooden stick or plastic broom handle to push the person away from the source. Once they are safe, call for emergency medical help immediately.
Mark breakdown: do not touch [1], switch off power or use non-conductive object [1], call for help [1]
Section E - Question 4
Model Answer:
Electrical appliances should not be used in the bathroom or near water because water is a good conductor of electricity. If an appliance falls into water or is touched with wet hands, the current can flow through the water and into your body, causing a dangerous or fatal electric shock.
Mark breakdown: water is a conductor [1], risk of electric shock [1]
Section F - Question 1
Model Answer:
The two electrical safety hazards are:
(1) The frayed power cord with visible internal wires on the toaster.
(2) The overloading of a single wall socket by plugging in multiple high-power appliances (toaster, kettle, microwave, and fan) into one adapter.
Mark breakdown: frayed cord [1], overloaded socket [1]
Section F - Question 2
Model Answer:
A frayed cord is dangerous because the exposed internal wires can come into contact with a person's skin, causing an electric shock. The exposed wires can also touch each other or metal surfaces, leading to a short circuit, which may cause sparks, burns, or fire.
Mark breakdown: risk of electric shock [1], risk of short circuit or fire [1]
Section F - Question 3
Model Answer:
If all four high-power appliances are used at the same time from one socket, the total current drawn will exceed the safe limit for that socket and wiring. This can cause the wires to overheat, the insulation to melt, and may result in an electrical fire. The circuit may also trip or a fuse may blow if a safety device is present.
Mark breakdown: current exceeds safe limit [1], overheating of wires [1], risk of fire [1]
Section F - Question 4
Model Answer:
Nomsa should:
(1) Stop Bongani from using the toaster and unplug it immediately to prevent electric shock.
(2) Reduce the number of appliances plugged into the single adapter or spread them across different sockets to avoid overloading.
Mark breakdown: stop use of frayed toaster [1], reduce socket overload [1]
Section G - Question 1
Model Answer:
A two-pin plug has only a live and a neutral pin, and does not have an earth connection. A three-pin plug has live, neutral, and an earth pin, which connects the metal casing of the appliance to the ground for safety. The three-pin plug is safer for high-power appliances like stoves or geysers because these appliances have metal casings that could become live if there is a fault, and the earth wire provides protection against electric shock.
Mark breakdown: difference explained [1], three-pin has earth wire [1], safer for high-power appliances [1]
Section G - Question 2
Model Answer:
If a fault occurs and the live wire touches the metal casing of an appliance, the casing becomes live and dangerous to touch. The earth wire provides a low-resistance path for the current to flow directly into the ground instead of through the user's body. This causes a large surge of current that will blow the fuse or trip the circuit breaker, cutting off the electricity supply and preventing electric shock. Without the earth wire, the user could receive a fatal shock when touching the casing.
Mark breakdown: live wire touches casing [1], earth wire provides path to ground [1], large current blows fuse/trips breaker [1], prevents shock to user [1]
Section G - Question 3
Model Answer:
A residual current device (RCD) is a sensitive safety switch that monitors the balance of current flowing in the live and neutral wires. If there is any leakage of current (for example, through a person's body or a fault), the RCD detects the imbalance and cuts off the power supply very quickly (within milliseconds). This is important because it can prevent fatal electric shocks, especially in situations where a person touches a live wire or faulty appliance. RCDs are particularly valuable in homes because they provide an extra layer of protection beyond fuses and circuit breakers.
Mark breakdown: definition of RCD [1], detects current imbalance [1], cuts power quickly [1], prevents fatal shocks [1]
Section G - Question 4
Model Answer:
Using an appliance with a damaged plug or faulty wiring is very dangerous because it can lead to electric shock, short circuits, sparks, and electrical fires. The damaged parts may expose live wires, allow current to leak, or cause poor connections that overheat. Before using such an appliance, it is essential to have it inspected and repaired by a qualified electrician. If repair is not possible, the appliance should be replaced. Never attempt to use or fix a faulty appliance yourself, as this puts you and others at serious risk.
Mark breakdown: risks identified (shock, fire, short circuit) [2], must be repaired by electrician or replaced [1], never use faulty appliance [1]
Mark Allocation Summary
