10th SCIENCE REFRESHER COURSE 5 Answer key

EVALUATION

I.  Choose the correct 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) Gunmetal   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 fi ld resembles that of an imaginary _____

a) U-Shaped magnet

c)  Solenoid coil

5. MRI stands for _____

b) Straight conductor carrying current

d) Bar magnet

a) Magnetic Resonance Imaging                      b) Magnetic Running Image

c)   Magnetic Radio Imaging

6. A compass is used for _____

a) Plotting magnetic lines

c)  Navigation

II. Fill in the blanks

d) Magnetic Radar Imaging

b) Detection of magnetic fi ld

d) All of these

1.  The magnetic strength is ______      at the poles.                                      maximum

2.  A magnet has _____ magnetic poles.                                  two

3.  Magnets are used in _____           for generating electricity.                                                              dynamos

4. Electromagnets                         ______             are used to lift heavy iron pieces.

5. A freely suspended bar magnet is always pointing along the ____ geographic north-south                                  direction.

6.  Like poles of magnets repel while unlike poles _____      attract

7.  The force of attraction of a magnet is ____ at the poles.

more

8.  Now a days, magnets are used to generate ______     in dynamos.                                     current

9.  Magnets are used in computers in the storing devices such as hard disks.  They are used in _____ and ____ cards also.

IV. Answer briefly

1. What is the formula for calculating the images formed between plane mirrors?

2. Differentiate : Concave mirror and Convex mirror.