Magnetism

Samacheer Book Back Questions And Answers For Science Standard 8 “Magnetism“

I. Choose the best answer:
1. A magnet attracts _____.
a) wooden materials
b) any metal
c) copper
d) iron and steel

2. One of the following is an example for a permanent magnet.
a) Electromagnet
b) Mumetal
c) Soft iron
d) Neodymium

3. The south pole of a bar magnet and the north pole of a U-shaped magnet will _____.
a) attract each other
b) repel each other
c) neither attract nor repel each other
d) None of the above

4. The shape of the Earth’s magnetic field resembles that of an imaginary _____.
a) U-shaped magnet
b) straight conductor carrying current
c) solenoid coil
d) bar magnet

5. MRI stands for _____.
a) Magnetic Resonance Imaging
b) Magnetic Running Image
c) Magnetic Radio Imaging
d) Magnetic Radar Imaging

6. A compass is used for _____.
a) plotting magnetic lines
b) detection of magnetic field
c) navigation
d) All of these

II. Fill in the blanks:
1. The magnetic strength is _____ at the poles.
2. A magnet has _____ magnetic poles.
3. Magnets are used in _____ for generating electricity.
4. _____ are used to lift heavy iron pieces.
5. A freely suspended bar magnet is always pointing along the _____ north-south direction.

Answers:
1. maximum
2. two
3. dynamos
4. Electromagnets
5. geographic

III. Match the following:
1. Magnetite A. Magnetic lines
2. A tiny pivoted magnet B. Natural magnet
3. Cobalt C. Compass box
4. Closed curves D. Ferromagnetic material
5. Bismuth E. Diamagnetic material

Answers:
1. B
2. C
3. D
4. A
5. E

IV. Consider the statements given below and choose the correct option:
1. Assertion: Iron filings are concentrated more at the magnetic poles.
Reason: The magnets are so sharp.
a. Both assertion and reason are true and reason is the correct explanation of assertion.
b. Both assertion and reason are true, but reason is not the correct explanation of assertion.
c. Assertion is true, but reason is false.
d. Assertion is false, but reason is true.

2. Assertion: The Earth’s magnetic field is due to iron present in its core.
Reason: At a high temperature a magnet loses its magnetic property or magnetism.
a. Both assertion and reason are true and reason is the correct explanation of assertion.
b. Both assertion and reason are true, but reason is not the correct explanation of assertion.
c. Assertion is true, but reason is false.
d. Assertion is false, but reason is true.