Fuse

Q.

Name th material used for making a fuse wire. Give a reason.

Q.

During short circuit, the current increases drastically at the short-circuit spot.

1. Reduces substantially

2. Does not change

Q. An electric fuse works on the principle of Joule's law of heating.

1. True
2. False

Q. Explain what is short circuiting an electric supply.

Q.

Explain the importance of using in a household electic circuit (i) fuse, and (ii) earthing wire.

Q.

List two methods of producing magnetic fields.

Q. An MCB works on the principle of ___ effect of electric current.

1. chemical
2. heating
3. magnetic
4. gravitational

Q. Why is a fuse wire used in domestic electrical circuits despite the presence of an earthing wire?

1. To increase current.
2. To increase voltage.
3. To reduce heating due to current.
4. To increase protection of electrical appliances.

Q.

An electric fuse works on the:
(a) chemical effect fo current
(b) magnetic effect fo current
(c) lighting effect of current
(d) heating effect fo current

Q.

Name the device used these days in place of electric fuses in electrical circuits.

Q.

In household circuits, a fuse is connected in series or in parallel?

Q.

Name two safety measures commonly used in electric circuits and appliances. Explain one of the measures in brief. [3 MARKS]

Q.

(a) Of what substance is the fuse wire made ? Why ?

(b) Explain why, a copper wire cannot be used as a fuse wire.

Q. Overloading can occur due to an accidental hike in

1. voltage
2. All of the above.
3. current
4. resistance

Q.

Can a 5 A fuse be used in wire carrying 15 A current? Why? [2 MARKS]

Q.

What type of electric fuse is used in electical appliances like car stereos ? Explain with the help of a labelled diagram.

Q.

If fuses of 250 mA, 500 mA, 1 A, 5 A and 10 A were availble, which one would be the most suitable for protecting an amplifier rated at 240 V, 180 W ?

Q.

A fuse is always connected with the electrical circuit in

1. parallel.

2. series.

3. both in series and parallel.

4. none of these

Q.

A 3-pin mains plug is fitted to the cable for a 1 kW electric kettle to be used on a 250 V a.c. supply. Which of the following statement is not corrent ?

(a) The fuse should be fitted in the live wire

(b) A 13 A fuse is the most appropriate value to use

(c) The neutral wire is coloured black

(d) The green wire should be connected to the earth pin.

Q.

State Joule’s law of heating.

Q.

In a safety fuse, the temperature to which the wire gets heated does not depend upon

1. the radius of the wire

2. the length of the fuse wire

3. the type of alloy used

4. the magnitude of the current

Q.

(a) Why are fuses fitted in the fuse box of a domestic electricity supply ?

(b) What device could be used in place of the fuses ?

Q.

A house wiring supplied with a $220\mathrm{V}$ supply line is protected by a fuse of $9\mathrm{A}$. Find the maximum number of bulbs ( $60\mathrm{W}$ each) connected in parallel that can be turned on.

Q.

(a) When does a fuse cut off current ? How does it do it ?

(b) What is the maximum number of 60 W bulbs that can be run from the mains supply of 220 volts if you do not want to overload a 5 A fuse ?

Q.

In normal use, a current of 3.5 A flows through a hair dryer. Choose a suitable fuse from the following :

(a) 3 A (b) 5 A (c) 10 A (d) 30 A

Q. Question 2
An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.

Q. An electric fuse works on the principle of Joule's law of heating.

1. False
2. True

Q. Fuse wire must have melting point than the circuit wire.

1. higher
2. lower
3. equitable

Q.

What is the usual capactiy of an electric fuse used (i) in the lighting circuit, and (ii) in the power circuit, of a small house ?

Q.

Explain how the fuse melts when a short circuit appliance gets earthed.