Physics Practical Electricity

What is the formula to calculate Power for electricity?

P = IV

What is the formula to calculate Energy

E = VIt

I: Current

V: Voltage

t: time

What are some dangers of electircity?

1. Damaged Insulation

2. Overheating Of Cables

3. Damaged Insulation

What are the dangers of damaged insulation?

• Live wire touches one another and cause a short circuit

• Short circuit causes metal casing to become live/cause a fire due to overheating

What are the dangers of overheating of cables?

• Cause fires

• Insulation may be damaged leading to short circuits

What are the dangers of damp conditions?

Current can be conducted by water which can cause electric shock

What are some safety features of electrical appliances?

1. Main switches

2. Miniature Circuit Breakers (MCB)

3. Earth Leakage Circuit Breaker (ELCB)

How do main switches make using electricity safer?

It turns off and on the electricity supply to the whole house

How do MCB make using electricity safer?

Has an electromagnetic switch that breaks the circuit when a large current from the main power supply is flowing through it.

How does the ELCB make using electricity safer?

Has an electromagnetic switch that breaks the circuit when current leakage is 30mA or more through the earth wire.

How does earthing the metal case of electrical appliances ensure that users do not get shocked?

The earth wire provides a route for the current to flow to the ground if live wire accidentally touches the metal casing of the appliances.

What is the use of a fuse?

Prevents the overheating of cables and electrical appliances due to large current flowing through it.

Why is the fuse rating slightly higher than the current in the electrical appliance and how does this prevent the overheating of electrical appliances?

Because the wire in the fuse will melt when the current exceeds its rating. Hence, it would cause the large current to be cut off from the power supply to avoid overheating of cables and electrical appliances.

What does double insulation do?

It covers the insulator in a layer of plastic, ensuring the metal parts are not exposed to users.

How does double insulation ensure users’ safety?

It prevents the electrical appliance with a metal casing from becoming live because the materials used to cover it are insulators, ensuring that users will not receive electric shock if the appliance is faulty.

What does a three-pin plug consist of?

1. Live wire

2. Neutral wire

3. Earth wire

What Is the colour of the live wire?

Brown

What is the colour of the Neutral wire?

Blue

What is the colour of the earth wire?

Green & Yellow

What is the function of a live wire?

A live wire conducts current from the mains supply to the appliances

What is the function of the Neutral wire?

It conducts current back to the mains supply from the appliances.

Why are safety devices in a circuit (fuses, switches & circuit breakers) connected to a live wire?

They can disconnect the live wire from carrying high voltages if a fault occurs. This ensures that the appliance is at a low voltage, causing no current to flow through and prevents the user from an electric shock.