House Wiring

Q.

What do you mean by power rating of an electrical appliance? How do you use it to calculate (a) the resistance of the appliance, and (b) the safe limit of current in it, while in use?

Q.

An electric ___ is a safety device, used to protect electrical appliances connected to the circuit.

Q.

Why is the earth pin thicker and longer than the live and the neutral pins? What is the advantage of earth wire connection in domestic appliances? [3 MARKS]

Q.

Name the commercial unit of electrical Energy. How it is related to its SI unit?

1. Kilowatt hour, 1kWh = 3.6 × 10⁵ joule

2. Kilowatt, 1kW = 36 × 10⁵ joule

3. Kilowatt hour, 1kWh = 3.6 × 10⁶ joule

4. Kilowatt second, 1kWs = 36 × 10⁵ kjoule

Q.

An appliance has three wires of colors red, black and green, and is connected to a three pin plug. The thickest pin is connected to which wire?

1. All pins have the same thickness

2. Red

3. Black

4. Green

Q.

Why we need a $5A$ fuse for an electric iron which consumes $1\mathrm{kW}$ power at $220V$?

Q.

(i) State and define the household unit of electricity.
(ii) What is the voltage of the electricity that is generally supplied to a house?
(iii) What is consumed while using different electrical appliances, for which electricity bills are paid?

Q.

Name the safety devices which are connected to the live wire of a household electrical circuit.

1. A switch and Earthing Wire

2. A fuse and Earthing Wire

3. A switch and a safety fuse

4. A switch and Neutral Wire

Q.

Which of the following devices is used to prevent the flow of excess current in a circuit?

1. Fuse

2. Switch

3. Bulb

4. Battery

Q. The safety device used to protect electrical appliances from harmful currents is

1. electric fuse
2. capacitor
3. inductor
4. resistor

Q.

The electrical gadgets used in a house such as bulbs, fans, heater, etc., are always connected in parallel, NOT in series.

The reason for connecting them in parallel is:

1. All appliances operate simultaneously

2. All appliances operate at the same voltage

3. All appliances operate at the same voltage and current

4. All appliances operate at the same current

Q.

For earthing an electric appliance, one has to remove the paint from the metallic body of the appliance where the electric contact is made. Explain the reason.

Q.

The electrical gadgets used in a house such as bulbs, fans, heater, etc., are always connected in parallel, not in series. Give two reasons for connecting them in parallel.

Q.

Give reason: An electric bulb gets fused when it is connected across a supply of voltage higher than its rating.

Q.

How should the several electric lamps be connected with the mains so that the switching on or off a lamp has no effect on the operation of other lamps?

Q.

Why is the fuse absolutely necessary in a power circuit?

Q. An electric heater is rated $1500W$. How much energy does it use in $10hours$ ?

1. $25kWh$
2. $10kWh$
3. $15kWh$
4. $12kWh$

Q. Question 16
Which uses more energy, a 250 W TV set in 1 h, or a 1200 W toaster in 10 minutes?

Q.

Of the three connecting wires in a household circuit:

In which of the three wires should the switch be connected?

Q.

Which part of an electrical appliance is earthed?

1. The part in contact with the live wire

2. The inner circuit of the appliance

3. The outer metallic case of the appliance

4. The part in contact with the neutral wire

Q. An electric heater of power $3kW$ is used for $10h$. How much energy does it consume? Express your answer in joule.

1. $1.08\times {10}^5$
2. $1.08\times {10}^8$
3. $1.08\times {10}^7$
4. $1.08\times {10}^3$

Q. The thick long pin in a three pin plug is connected to the

1. live wire
2. earth wire
3. neutral wire
4. kWh wire

Q.

Name two systems of power distribution in a household circuit.

Which of the system named above is superior and why?

Q. Pick the odd one out from the following with respect to a household electrical wiring system.

1. Refrigerator
2. kWh meter
3. MCB
4. Earth wire

Q.

what is the meaning of open circuit

Q.

Of the three connecting wires in a household circuit
(i) Which two of the three wires are at the same potential?
(ii) In which of the three wires should the switch be connected?

Q.

A fuse has a current rating of $5A$. Can it be used for a heater of rating $1kW,220V$ ?

Q. Which of the following does a domestic wiring system consists.

1. Electric meter and a main switch
2. Main switch
3. Lighting circuit
4. Power circuit

Q.

Differentiate between the following.

Series circuit and parallel circuit.

Q.

Why is the series arrangement not used for domestic circuits?