NCERT Class VII Science Solutions: Chapter 14-Electric Current and its Effects Part 3

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SHORT ANSWER QUESTIONS

Question 13:

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

Answer:

No, a geyser and a television set require different amount of current. Therefore the fuse used in these will be of different ratings.

Question 14:

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

Answer:

Heating effect – Geyser, room heater

Image of Geyser, Roomheater

Geyser, Roomheater

Image of Geyser, Roomheater

Magnetic effect – Electric bell, Cranes to lift magnetic material.

Image of electric bell

Electric Bell

Image of electric bell

Question 15:

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

Answer:

The child may put his/her fingers into the socket and he/she may get an electric shock which could be fatal.

Question 16:

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.

Answer:

Paheli’s electromagnet will attract more pins as it has more number of turns of wire on it and thus a stronger electromagnet.

LONG ANSWER QUESTIONS

Question 17:

Your teacher has shown you the following activity.

As showing in images is a shown you the following activity.

Shown You the Following Activity.

As showing in images is a 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 arc connected to a cell through a switch as shown in the Figure. 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.

Answer:

Some of the questions can be

  1. Why does the nail attract the pins?

  2. What will happen if we connect more cells in the circuit?

  3. What will happen if we use some other material like a straw in place of the nail?

  4. What will happen if we wrap the wire on the nail more tightly?

    Or

    Any other appropriate question