Solution of Chapter 14. Electric Current and Its Effects (NCERT - Exemplar Science Book)

When an electric current flows through a copper wire AB as shown in Figure14.1, the wire

Choose the statement which is not correct in the case of an electric fuse.

Three bulbs A, B, C are connected in a circuit as shown in Figure 14.2. When the switch is ‘ON’

When a switch is in OFF position,

(i) circuit starting from the positive terminal of the cell stops at the switch.

(ii) the circuit is open.

(iii) no current flows through it.

(iv) current flows after some time.

Choose the combination of correct answer from the following.

Which of the following precautions need not be taken while using electric gadgets/appliances/circuit?

Which property of a conducting wire is utilized in making electric fuse?

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

Fill in the blanks:

(i) Our body is a ________________ of electricity.

(ii) An electric cell produces electricity from the __________ ___________ in it.

(iii) In an electric circuit a fuse is a _________ _______ to prevent possible fire.

(iv) A combination of two or more cells is called a _________.

Unscramble the following words:

(i) TBTAYER

(ii) SFEU

(iii) HTRCO

(iv) HICWTS

Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel in the night to get dim light. Has she taken the right step? Give one reason to justify your answer.

Why are compact fluorescent lamps (CFLs) preferred over electric bulbs?

Why is an electric fuse required in all electrical appliances?

Can we use the same fuse in a geyser and a television set? Explain.

Name two electric devices for each were (i) heating effect of the current is used and (ii) the magnetic effect of current is used.

Why do we cover plug pin holes which are within the reach of children with cellotape or a plastic cover when not in use?

Boojho made an electromagnet by winding 50 turns of wire over an iron screw. Paheli also made an electromagnet by winding 100 turns over a similar iron screw. Which electro magnet will attract more pins? Give reason.

Your teacher has shown you the following activity.

Activity: Teacher has wound a long insulated piece of wire around an iron nail in the form of a coil. Free ends of the wire are connected to a cell through a switch as shown in the Figure 14.3. The current is switched on and some pins are placed near the ends of the nail.

Write down any three questions that come to your mind about this activity.

Paheli took a wire of length 10 cm. Boojho took a wire of 5 cm of the same material and thickness. Both of them connected the wires as shown in the circuit given in Figure 14.4. The current flowing in both the circuits is the same.

(i) Will the heat produced in both the cases be equal? Explain.

(ii) Will the heat produce be the same if the wires taken by them are of equal lengths but of different thickness? Explain.

How does the magnetic effect of electric current help in the working of an electric bell? Explain with the help of a diagram.

Draw the symbols of the following circuit components.

(i) electric cell

(ii) switch in off position

(iii) electric bulb

(iv) battery