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# Class 10 FRANK Solutions Physics Chapter 4.2 - Electrical Power and Household Circuits

Revise concepts using Frank Solutions for ICSE Class 10 Physics Chapter 4.2 Electrical Power and Household Circuits. Revise the differences between electrical energy and electric power. In addition, the chapter concepts you can learn from Frank Solutions include fuse, Joule’s law, electrical resistance, earthing etc.

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## Electrical Power and Household Circuits Exercise 187

### Solution 1

Electrical power is defined as the rate at which energy is changed or work is done i.e., the work done per second or energy converted per second.
Electrical appliances come with certain number of watts and volts written on them. Power rating of an electrical appliance gives the knowledge of the safe current limit of an appliance and also indicates the voltage above which the appliance should not be used.

### Solution 4

'The current rating of a fuse is 5 A' means that the maximum safe current permitted to flow through it before it breaks down is 5A.

### Solution 9

An electric fuse is a safety device which is used to limit the current in an electric circuit. The use of a fuse thus safeguards the circuit and appliances connected in that circuit from being damaged.
A fuse is generally made of an alloy of lead and tin.

### Solution 10

Characteristics of fuse wire:
(i) It should have low melting point.
(ii) It should have high resistance.

### Solution 11

(i) resistance, melting point
(iii) series, live

## Electrical Power and Household Circuits Exercise 188

### Solution 15

The main fuse is connected between the kWh meter and distribution board of the house circuit. The main fuse is connected in the live wire.

### Solution 16

Yes, kWh is the unit of electrical energy.

### Solution 17

A switch is an on-off device for current in a circuit (or in an appliance). Its main function is either to connect or to disconnect an electrical appliance in an electric circuit.
Switches are always connected in the live wire of circuits so that when a switch is in 'off' position, no current flows through the appliance and its live and neutral wires are at same potential and it is safe to touch the live wire leading to the appliance, even when the fuse is blown.

### Solution 18

A switch should not be touched with wet hands. This is because water forms a conducting layer between the hand and the live wire of the switch through which the current passes to the hand and we may get a fatal shock.

### Solution 20

The metal case of an electrical appliance is earthed so that in any case of accidental contact of live wire with the metallic body of the appliance, the earthing would provide a safe and easy path for the electric charges to flow down to the earth which acts as very large sink. Thus, user is thereby protected from any fatal electric shock.

### Solution 22

International convention of colour coding:
1. Live wire - Brown
2. Neutral wire - Light blue
3. Earth wire - Green or yellow

### Solution 25

The fuse helps to control the maximum current in an electrical circuit. The fuse protects an electrical circuit by melting and breaking the circuit, whenever the current exceeds the pre-determined limit in the circuit. Due to low melting point, the fuse wire melts and then breaks the circuit.

### Solution 26

Earthing is done to save an electrical circuit or an appliance from damage. If due to some reason such as short circuiting, an excessive current flows through the line wires, it will pass to the earth if there is local earthing, otherwise it may cause a fire due to overheating of line wires.

### Solution 28

One may get an electric shock from an electrical appliance if accidentally the live wire comes in contact with the metallic case of the body of the appliance due to break of insulation after constant use (or otherwise).

### Solution 29

The SI unit of electrical energy is joule.
The SI unit of electrical power is watt.
(i) Kilowatt-hour is the household unit of electrical energy. It is defined as the quantity of electrical energy consumed in 1 hour when the rate of consumption is 1000 watts, i.e. 1000 J/s.
(ii) A voltage of 220 volt is generally supplied to a house.

### Solution 32

A three pin-plug has three terminals:
(i) Earth pin: It provides connection for earthing.
(ii) Neutral pin: It provides connection to the neutral wire.
(iii) live pin: It provides connection to the live wire.

### Solution 33

Consumer pays the bill in kilowatt-hour.

### Solution 35

Kilowatt-hour is the commercial unit of electricity.

### Solution 37

Power-voltage rating of an electrical appliance indicates the value of voltage above which the appliance should not be used. It serves as a precaution to the customer and also helps to calculate the maximum value of current that can be safely passed through the appliance.

### Solution 38

The physical quantity is electric power.

### Solution 39

It means that if the bulb is lighted on a 200V supply it consumes 60W electrical power or 200J of electrical energy converts into heat and light in 1 second.

## Electrical Power and Household Circuits Exercise 189

### Solution 41

We know,

P = VI

Thus,

I = P/V = 40/220 = 0.18 A

### Solution 42

Watt-hour is the commercial unit of electrical energy.
One watt-hour is the electrical energy consumed by an electrical appliance of power 1 watt when it is used for 1 hour.
1Wh = 3600 J

### Solution 43

Kilowatt-hour is the commercial unit of electricity.