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Class 7 science chap 14 additional Questions-answer

Chapter 14: Electric current and its Effects

Additional Questions

Objective Questions

A. Write whether the following statement is True/False:

a. An electric cell has only a negative terminal.

b. An electric bell works on the magnetic effect of current.

c. The circuit is complete when the switch is in OFF position.

d. The wire of an electric bulb is made of tungsten.

e. LED bulbs consume more electricity as compared to CFL.

f. The electromagnets are not used to separate magnetic material from the junk.

Answers a. False b. True c. False d. True e. False f. False

B. Match the following:

Answers 1. b 2. d 3. a 4. C

C. Fill in the blanks:

1. An electric bulb glows only when the switch is in the_______ position.

2. The core of a _______ is made from iron.

3. Human body is a _________ of electricity.

4. Electromagnets are better than the ________.

5. A __________ is an electric path which begins from the positive terminal of a cell and terminates at the negative terminal.

6. ________ is a mark for which we should look at an electrical appliance before buying.

Answers

1. ON

2. Electromagnet

3. Good conductor

4. Permanent magnets

5. Closed-circuit

6. ISI mark

A. Very Short Questions

I. Name any two devices that work on the principle of the magnetic effect of current.

II. Name any two devices that work on the principle of heating effect of current.

III. Name the device used these days in place of fuse in electrical circuits.

IV. Why the use of CFLs is preferred over electric bulbs?

V. Which type of wire is used in an electric fuse?

VI. Give an advantage of MCB.

VII. What do you mean by electric current?

Answers

I. Electric bell and loudspeaker work on the principle of the magnetic effect of current.

II. Geyser and electric heater work on the principle of heating effect of current.

III. MCB is used these days in place of fuse in electrical circuits

IV. CFLs are preferred over electric bulbs because CFLs consume less power of electricity than electric bulbs.

V. An electric fuse is always connected with a live wire.

VI. MCB is more sensitive to current than a fuse.

VII. An electric current is a flow of electric charge in a circuit.

B. Short Questions

I. What is the benefit of electromagnets over the permanent magnets?

II. Explain why we should not touch the glowing bulb?

III. What is MCB? How does it work?

IV. What happens when the live wire and neutral wire touch each other?

V. Write some components of the electric circuit?

VI. What is CFL?

Answers

I. An electromagnet can be switched ON or OFF as desired and this is not possible in permanent magnets. That’s why the electromagnets are better than the permanent magnets.

II. We should not touch the glowing bulb directly because it is connected to the main supply, as it can be very hot and can burn our hand as well.

III. MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowed limit. MCB does on not work on the heating effect of current as it works on the magnetic effect of current.

IV. When the live wire and neutral wire touch each other than the short circuit occurs, due to which a large current flow through the wires of the house and this results in the heating of the wires to a high temperature and a fire may be started.

V. The commonly used electrical components are

a. Electric cell

b. Electric bulb

c. Battery

d. Wire

e. Switches

VI. CFL is a fluorescent lamp designed to replace an incandescent light bulb. It consumes less power of electricity than electric bulbs. CFLs are less expensive in the long run because they last much longer than electric bulbs.

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