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Physics [3 Mark Question Answer]

Electrical Power and Household Circuits · ICSE STD 10 (ICSE - English Medium). 12 questions.

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[3 Mark Question Answer]

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12 questions · timed · auto-graded

Question 13 Marks

In following figure shows two bulbs with switches and fuse connected to mains through a socket.Name and state the colour of insulation of each wire 1, 2 and 3.

Answer
Wire no Wire name Colour (Old convention) Color (New convention)
1 Neutral wire Black Light blue
2 Earth wire Green Green or yellow
3 Live wire Red Brown
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Question 23 Marks
Name the device used to protect the electric circuits from over loading and short circuit. On what effect of current does it work?
Answer
An electric fuse is a safety device, which is used to limit the current in an electric circuit. The use of fuse safeguards the circuit and appliances connected in that circuit from being damaged. An alloy of lead and tin is used as a material of fuse because it has low melting point and high resistivity.
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Question 33 Marks
A power circuit uses a cable having three different wires.
(a) Name the three wires of the cable.
(b) to which of the two wires should the heating element of an electric geyser be connected?
(c) To which wire should the metal case of the geyser be connected?
(d) to which wire should the switch and fuse be connected?
Answer
(a) The three wires are: Live wire, Earth wire and Neutral wire.
(b) The heating element of geyser should be connected to live wire and neutral wire.
(c) The metal case should be connected to earth wire.
(d) The switch and fuse should be connected to live wire.
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Question 43 Marks
What is the colour code for the insulation on the (a) live (b) neutral and (c) earth wire?
Answer
According to new international convention
(a) Live wire is brown in colour.
(b) Neutral is light blue and
(c) Earth wire is yellow or green in colour.
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Question 53 Marks
(a) the earthing of an electric appliance is useful only if the fuse is in the love wire. Explain the reason.
(b) Name the part of the appliance which is earthed.
Answer
(a) The fuse must be connected in the live wire only. If the fuse is in the neutral wire, then although the fuse burns due to the flow of heavy current, but the appliance remains at the supply voltage so that on touching the appliance current flows through the appliance to the person touching it.
(b) Metallic case of the appliance should be earthed.
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Question 63 Marks
The following diagram shows a three pin socket marked as 1, 2 and 3.



(a) Identify and write live (L) neutral (N) and earth (E) against the correct number
(b) To which part of the appliance is the terminal 1 connected?
(c) To which wire joined to 2 or 3, is the fuse connected and why?
Answer
(a) 1 – Earth, 2 – Neutral, 3 – Live
(b) Terminal 1 is connected to the outer metallic case of the appliance.
(c) The fuse is connected to live wire joined to 3 so that in case of excessive flow of current fuse melts first and breaks down the circuit to protect appliances.
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Question 73 Marks
What is a fuse? Name the material of fuse. State on characteristic of material used for fuse.
Answer
An electric fuse is a safety device, which is used to limit the current in an electric circuit. The use of fuse safeguards the circuit and appliances connected in that circuit from being damaged.
An alloy of lead and tin is used as a material of fuse because it has low melting point and high resistivity.
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Question 83 Marks
Draw a Labelled Diagram of a Three Pin Socket.
Answer


E: for earth pin
N: for neutral wire pin
L: for live wire pin.
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Question 93 Marks
What purpose is served by the terminals of a three way pin plug? Draw a diagram and name the pins
Answer
All electrical appliances are provided with a cable having a plug at one end to connect the appliance to the electric supply.
In this three way pin plug, the top pin is for earthing (E), the live pin (L) in on the left and the neutral pin (N) is on the right.
Image
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Question 103 Marks
At what voltage is the electric power from the generating station transmitted? Give reason to your answer.
Answer
Electric power from the generating station is transmitted at $11 kV$ because voltage higher
than this causes insulation difficulties, while the voltage lower than this involves high
current and loss of energy in form of heat $\left(I^2 R t\right)$.
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Question 113 Marks
State one advantage of using the main switch in house wiring.
Answer

The main switch is a double pole switch with an iron covering.

The major advantage of using a main switch is that it can break the connection of both, the live and the neutral wire at the same time.

This protects electrical appliances from accidental damage due to electrical faults.

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Question 123 Marks
In what unit does the electric meter in a house measure the electrical energy consumed? What is its value in S.I unit?
Answer
The domestic electric meter measure the electrical consumption in kilowatt-hour (kwh).$1$ kWh $= 1$ kilowatt $\times 1$ hour
$= 1000 Js^{-1} \times (60 \times 60) s$
$= 3.6 \times 10^6 J$ in S.I. unit.
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[3 Mark Question Answer] - Physics STD 10 Questions - Vidyadip