Electrical Safety

Question 1

What are the effects of Electrical Current on the body?

Answer 1

Burns
Muscle contractions
Death
Ventricular Febrilation

Question 2

Name 2 Design features that protect the user

Answer 2

Earthing

Double insulation

Question 3

What is earthing?

Answer 3

The earth wire creates a safe route for the current to flow through if the live wire touches the casing.
The earth terminal is connected to the metal casing so that the current goes through the earth wire instead of causing an electric shock. A strong current surges through the earth wire because it has a very low resistance. This breaks the fuse and disconnects the appliance.

Question 4

What is double insulation?

Answer 4

Insulating the live wire on two levels, ensuring their is no way the live source can touch the user

Question 5

Draw an earthing circuit diagram

Answer 5

Circuit showing live wire going into product, with earth wire clearly visible passing into ground and back to sub station

Question 6

What is an RCD breaker circuit?

Answer 6

Residual Current Device: a device that prevents fatal electric shocks by switching power off automatically. Does this by monitoring current flowing through neutral and live wires.

Question 7

Show how an RCD breaker works using diagrams

Answer 7

1st circuit: current flowing through live and leaving circuit through neutral terminals. Magnetic field on coils is equal on both coils therefore the iron magnetic pivot stays in position with a closed switch.
2nd faulty circuit: fault in appliance causes current to drop in neutral wire, as some current is leaving the circuit down the earth wire in the appliance. This current imbalance causes the magnetic field from the neutral coil to decrease, meaning the iron pivot is tilted down toward the live coil and the circuit is broken, switching power off.