Electricity II

Question 1

What is the SI unit for power?

Answer 1

Watt

Question 2

What is the definition of power?

Answer 2

It is the conversion of electrical energy by a component into other forms of energy in one second.

Question 3

What are the 3 formulas to find power?

Answer 3

P= E/t (energy/time) 
P= V x I (voltage x current) 
P= WD/t (work done/ time)

Question 4

is 1W = I J/s ?

Answer 4

Yes it is, 1 watt means 1 joule of energy converted in one second.

Question 5

What is the unit for power when the question gives Watt/w ?

Answer 5

kWh

Question 6

What is the unit for power when the question gives time in seconds?

Answer 6

J/s

Question 7

What is the unit for power when the questions gives time in hour?

Answer 7

kWh

Question 8

Why is energy for household items measured in kWh?

Answer 8

It is because using the unit J (joules) is not suitable for measuring a relatively large amount of electrical energy consumed in households and offices. Hence, kWh is used.

Question 9

1kW = ?W

Answer 9

1000W

Question 10

1MW = ?W

Answer 10

1 000 000W

Question 11

1GW = ? W

Answer 11

1 000 000 000 W

Question 12

What is the formula for energy in joules?

Answer 12

E (J) = power(W) x time (s)

Question 13

What is the formula for energy in kW?

Answer 13

E (kW) = power (kW) x time (hours)

Question 14

How do you find the total cost of energy used?

Answer 14

Energy used (kWh) x cost per kWh

Question 15

What are the 3 dangerous use of electricity?

Answer 15

Overloading, damaged insulation and damp conditions.

Question 16

Explain how damp conditions result in one being electrocuted?

Answer 16

• Circuit in damp conditions has a lower resistance compared to dry conditions.
• This is because water provides a conducting path from the appliance to your body.
• A larger current flowing through the damp condition might be able to electrocute a person.

Question 17

What to avoid when you have electrical appliances in damp conditions.

Answer 17

1) Avoid getting water into the sockets of the appliance.

2) Do not use an appliance until you are sure it is dry.

Question 18

Explain how overloading can cause fire?

Answer 18

• Inserting too many plugs into the same power socket may draw a large current, exceeding the current being supplied by the outlet.
• The large current generates heat, which may melt the insulation and cause a fire.

Question 19

Explain how damaged insulation can electrocute someone and cause a fire?

Answer 19

• The wires is exposed when the insulation wears off.
• Different parts of the wire may touch each other resulting in a short circuit.
• When a short circuit happens, the resistance of the circuit becomes lower. As a result, a larger current flow through it.
• If a person touches the wire, current would flow through his or her body, causing and electric shock.
• A fire may also occur too.

Question 20

What are the 3 main wires in a 3 pin plug?

Answer 20

Live, Neutral, and Earth.

Question 21

What are the components in a 3 pin plug?

Answer 21

Fuse, Live wire, Earth wire, Neutral wire and cable grip/

Question 22

What is the color of the live wire?

Answer 22

Brown

Question 23

What is the color of the earth wire?

Answer 23

Green and blue

Question 24

What is the color of the Neutral wire?

Answer 24

Blue

Question 25

In the live wire, do you agree that there is voltage, if so, will there be current?

Answer 25

Yes, there is a voltage of 240V and current flows.

Question 26

In the Neutral wire, is there voltage and current.

Answer 26

There is current but no voltage.

Question 27

In the earth wire, there is voltage and no current, do you agree?

Answer 27

There is only voltage but no current if the appliance is working properly.

Question 28

Where is the earth wire connected to?

Answer 28

One side of it is connected to the metal casing, the other side to the earth.

Question 29

Where is the live wire connected to?

Answer 29

It is connected to the circuit breaker, fuse, switch.