Class 8 General Science Notes: - Unit-10: Electricity and Magnetism: Solved Exercise (Short Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

B. Short Questions

i). Why do electric devices need two conducting paths from a voltage source to operate?

Ans:

We need two conducting wires/paths because when we connect an electric device to a battery, the electrons released from the battery need to travel back to the positive terminal of the battery. So electrons need to travel in a complete circuit and they have to finish back where they started.

ii) Why do wires usually warm up when an electric current passes through them?

Ans:

This is because wires have certain electrical resistances. This is due to the collision of free electrons with the atoms of the wire resulting in an increase of the kinetic energy which causes the wire to heat up.

iii) During floor grinding and polishing repairs in your house, the fuse blows when the operator starts his heavy machine. He wants to replace a fuse with a piece of wire. Would you agree? Give a reason for your response.

Ans:

No, one should not be allowed to replace the fuse in the house with a piece of wire. This is because every wire cannot be used as a fuse wire. A fuse wire must have a low melting point, such that it could melt and break in response to a large amount of current.

iv) Explain why is it dangerous if we use a hair dryer in bathtub?

Ans:

Do not use electric appliances or cables to come into contact with water. If we use a hair dryer in the bathtub with our wet bodies it may cause electric shock. A wet body gives less resistance to the flow of current and current easily passes through the body to give an electric shock.

v) What advantage will a crane have with electromagnet over other cranes? Can it use as a permanent magnet?

Ans:

Electromagnets allow industries like scraps yard to work at a much more efficient rate and in turn, help them increase profit. No, it cannot be used as a permanent magnet due to frequent changes in current.

Unit-10: Electricity and Magnetism: Solved Short Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

************************************

Shortcut Links For:

1.  5th Class All Subjects Notes
2.  8th Class All Subjects Notes

1. Website for School and College Level Physics
(https://askrarequiz.blogspot.com)
2. Website for School and College Level Mathematics
(https://askraremaths.blogspot.com)
3. Website for Single National Curriculum Pakistan - All Subjects Notes
(https://askrareclassnotes.blogspot.com/)

© 2023 & onwards Academic Skills and Knowledge (ASK)

Note:  Write me in the comments box below for any query and also Share this information with your class-fellows and friends.