Electricity - 2.3.2 Mains Electricity (GCSE Physics AQA)

Mains Electricity

Connecting to the Mains

Cables

• Cables are used to connect to the mains. In order to use our electrical devices, we must connect them with cables to the mains supply. The cables will provide a pathway for the electricity to run through.
• The cables are made of three wires. Inside each cable are 3 wires, meaning that they are called three core cables. These all run into the head of a three pin plug, which can go into a wall socket.

The Three Wires

For AQA exams, we need to know the colours, potential difference and uses of each of three cable wires:

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Dangers of Electricity

Dangers of the Live Wire

• The live wire is very dangerous. The live wire has an alternating pd of 230V from the mains supply, making it very dangerous. The value of 230V is very far from the value of 0V, which is the normal voltage of the human body.
• The live wire causes shocks. Since the live wire has a very large potential difference compared to the human body, the live wire can cause shocks. When you touch a live wire, current flows through your body and causes an electric shock.
• Open circuits are still dangerous. Even if the switch is open in a circuit (i.e. the circuit is not complete), the circuit may not actually be safe. There might not be a current in the live wire, but there will still be a potential difference in it. When touched, a current can flow from the live wire through your body and into the earth.

Other Dangers of Electricity

• Water is dangerous around electricity. Water can conduct electricity, which means that it can provide a path for electricity to flow to your body. This can lead to electric shocks, and therefore it is essential to use dry hands when around electricity and when handling sockets.
• Fuses are important for safety. Sometimes electric circuits become overheated, and the amount of electricity flowing through is very large. This can lead to the circuit becoming very hot, which can potentially cause a fire. Fuses are devices which shut down the circuit if it the current becomes too high.
• Sockets and wires have insulating coating. Sockets have a plastic insulating coating, which prevents you from getting in direct contact with the mains supply. Wires also have this, but sometimes wires can become cut and frayed, exposing the dangerous live wire.