Electrical Systems

Question 1

What is electricity

Answer 1

Form of energy caused by flow of electrical charges
In metals, free moving electrons flow to conduct electricity

Question 2

What is electrical circuit

Answer 2

Path where electrical charges flow

Question 3

What is a short circuit

Answer 3

When a current flows through a path of negligible resistance. No current flows through the light bulb

Question 4

Why is a short circuit dangerous

Answer 4

A short circuit can result in a very large current, which can generate enough heat to start a fire.

Question 5

What is an electrical current

Answer 5

Rate at which electrical charges flow

Question 6

SI Unit for electrical current

Answer 6

Ampere
Written as A

Question 7

What is a conventional current

Answer 7

In closed circuit, current flows from positive to negative terminal

Question 8

What is electron flow

Answer 8

Electricity is a result of electrons flowing from negative to positive terminal

Question 9

How to measure current

Answer 9

Ammeter.
It is connected in series to circuit.
Negligible resistance

Question 10

How to read ammeter

Answer 10

Nearest half of smallest division

Question 11

Define potential difference

Answer 11

The potential difference between 2 points in an electrical circuit is the amount of energy needed to move a unit charge from one point to another

Question 12

SI unit for potential difference

Answer 12

Volt
Written as V

Question 13

Instrument to measure potential difference

Answer 13

Voltmeter
It is connected in parallel to (across) the component. Voltmeter has a very large resistance and does not allow any current to flow through

Question 14

How to read voltmeter

Answer 14

Nearest half of smallest division

Question 15

PRACTICAL: precision of ammeter in school

Answer 15

0.01A

Question 16

PRACTICAL: precision of voltmeter in school

Answer 16

0.05V

Question 17

What is resistance

Answer 17

Measure of how much the component opposes flow of electric current

Question 18

Factors affecting resistance

Answer 18

Smaller cross section, higher resistance
Longer wire, higher resistance
Type of material

Question 19

Current formula in series circuit

Answer 19

I=I1=I2=I3

Question 20

Voltage formula in series circuit

Answer 20

V=V1+V2+V3

Question 21

Effective resistance formula in series circuit

Answer 21

R=R1+R2+R3

Question 22

Current formula in parallel circuit

Answer 22

I=I1+I2+I3

Question 23

Voltage formula in parallel circuit

Answer 23

V=V1=V2=V3

Question 24

Relationship between resistors and effective resistance of circuit in parallel circuit

Answer 24

As resistors increase, the effective resistance decreases

Question 25

Effects of electric current

Answer 25

Heating Lighting Magnetic Chemical

Question 26

How to increase magnetic effect

Answer 26

Increase current flowing through the coil Increase number of turns of the coil Insert a soft iron core into the coil

Question 27

What is electroplating

Answer 27

Process of depositing a layer of metal on another substance using electrolysis

Question 28

What is power

Answer 28

Power is the amount of energy transferred or converted per unit time. (Rate of energy conversion)

Question 29

SI Unit for power

Answer 29

watt Written as: W

Question 30

Formula for amount of energy(J)

Answer 30

Power(W)*Time(s)

Question 31

Formula to calculate electric bills

Answer 31

Energy(kWh)=Power(kW)*Time(h)

Question 32

What are some electrical hazards

Answer 32

Electrical fires Electric shocks and electrocution

Question 33

How are electrical fires caused

Answer 33

Large currents can be drawn when electrical circuits are damaged, do not work properly or are misused. Too many plugs inserted into the same power socket Large current generates heat, which may melt insulation and even cause a fire

Question 34

Precautions for electrocution

Answer 34

Switch off and pull out plug from socket before cleaning electrical appliances Electrical appliances should be kept in dry places and handled with dry hands Call the electrician to repair damaged appliances or electrical cables as wires inside may be exposed Never overload or insert any item into an electrical socket

Question 35

Who is fuse connected to

Answer 35

Live wire

Question 36

How does fuse work

Answer 36

Excessive current (above fuse rating) will cause the fuse to melt This results in an open circuit

Question 37

How does circuit breaker work

Answer 37

When there is excessive current, the circuit breaker trips, leading to power turning off for that part