F2 - SEM1 - Circuit - 8.6 Household electricity - Part B

Question 1

What are the potential hazards in using electricity?

8.6 Household electricity

Answer 1

Overloading
Short circuits

8.6 Household electricity

Question 2

How to avoid overloading?

8.6 Household electricity

Answer 2

Connect electrical appliances draw large current to different mains sockets

8.6 Household electricity

Question 3

How does overloading occur?

8.6 Household electricity

Answer 3

• too many electrical appliances are connected to a main socket
• exceeds safety limit of a circuit

8.6 Household electricity

Question 4

What happen when the number of branches increases?

8.6 Household electricity

Answer 4

The current flowing through the cell decreases

8.6 Household electricity

Question 5

Fill in the blanks

Several appliances are connected to a single mains socket via ________

8.6 Household electricity

Answer 5

Several appliances are connected to a single mains socket via universal adaptor

8.6 Household electricity

Question 6

Does the bulb light up? Why?

8.6 Household electricity

Answer 6

No
The connecting wire provides a path with a very low (nearly zero) resistance. The current is more likely to flow through the wire than the bulb. The bulb is short-circuited.

8.6 Household electricity

Question 7

What happens to the nichrome wire?

8.6 Household electricity

Answer 7

The nichrome wire melt

8.6 Household electricity

Question 8

Fill in the blanks

A short circuit provides a path with ________ for current to flow
A short circuit causes ________ to flow in a circuit

8.6 Household electricity

Answer 8

A short circuit provides a path with _a very low resistance_ for current to flow
A short circuit causes _a large current_ to flow in a circuit

8.6 Household electricity

Question 9

What are the causes of short circuits in electrical appliances?

8.6 Household electricity

Answer 9

• a loose or worn wire
• dust and moisture on the circuit

8.6 Household electricity

Question 10

How to avoid short circuits?

8.6 Household electricity

Answer 10

keep electrical appliances clean and dry

8.6 Household electricity

Question 11

Why short circuit is dangerous and should be avoided?

8.6 Household electricity

Answer 11

Short circuit may overheat and damage an electrical appliance

8.6 Household electricity

Question 12

What are the 3 safety designs to protect circuits?

8.6 Household electricity

Answer 12

• Fuses
• Circuit breakers
• Earth wires

8.6 Household electricity

Question 13

Draw the circuit symbol

Fuse

8.6 Household electricity

Answer 13

8.6 Household electricity

Question 14

What is the purpose of fuse?

8.6 Household electricity

Answer 14

break a circuit when the current becomes too large
protects the circuit from the overheat current

8.6 Household electricity

Question 15

What is a fuse made of?

8.6 Household electricity

Answer 15

A metal wire with a low melting point

8.6 Household electricity

Question 16

What is the number printed on a fuse called? What does it mean?

8.6 Household electricity

Answer 16

fuse rating is the maximum current the fuse can stand

8.6 Household electricity

Question 17

What happens when the current is larger than the fuse rating?

8.6 Household electricity

Answer 17

The fuse will blow and cut off the current

8.6 Household electricity

Question 18

Fill in the blanks

A suitable fuse should having a rating ________ than the current passing through the electrical appliance when it is operating normally

8.6 Household electricity

Answer 18

A suitable fuse should having a rating _slightly higher than_ than the current passing through the electrical appliance when it is operating normally

8.6 Household electricity

Question 19

What should be done before replacing a blown fuse?

8.6 Household electricity

Answer 19

Fix the short circuit

8.6 Household electricity

Question 20

What happen to circuit breaker when a current exceeds the rating?

8.6 Household electricity

Answer 20

the circuit breaker turns to the OFF mode and cuts off the current

8.6 Household electricity

Question 21

How to reset circuit breaker?

8.6 Household electricity

Answer 21

switching the circuit breaker to ON mode

8.6 Household electricity

Question 22

What should you do if the circuit breaker keeps cutting off the circuit?

8.6 Household electricity

Answer 22

should ask a registered electrical worker to check the circuit

8.6 Household electricity

Question 23

What happen when the circuit becomes overloaded?

8.6 Household electricity

Answer 23

• Electricity failure
• a fire

8.6 Household electricity

Question 24

What is the purpose of Earth wire?

8.6 Household electricity

Answer 24

• Earth wire connects the metal case of an electrical appliance to the ground
• Protects us from electric shock

8.6 Household electricity

Question 25

What happen if you touch the metal case of an electrical appliance with a **damaged Live wire touches the metal case**? ## Footnote 8.6 Household electricity

Answer 25

You may be **hurt or even killed** by **electric shock** A **current** from the **live wire** will pass through **your body to the ground** ## Footnote 8.6 Household electricity

Question 26

List **4 Should** when using electricity ## Footnote 8.6 Household electricity

Answer 26

* Use **three-pin plugs with earth wire** * Switch on an electrical appliance only after **firmly plugging it into a socket outlet** * Use** fuses with suitable fuse ratings** * Ask a **registered electrical worker** to immediately replace damaged cables, sockets and plugs ## Footnote 8.6 Household electricity

Question 27

List **4 Should Not** when using electricity ## Footnote 8.6 Household electricity

Answer 27

* Overload sockets * Cover electrical appliance at work * Let water seep into any electrical appliance * Touch sockets or switches with wet hands as this can result in electric shock ## Footnote 8.6 Household electricity