Q1 of 45 Page 302

Fill in the blanks

i) For a motor: a permanent magnet, then commercial motor: _______


ii) Focal length of a lens; metre, then for power of a lens____________


(i) Electromagnet

Explanation: Electromagnets are much stronger than permanent magnets; moreover permanent magnets lose their magnetivity over time due to moisture and heat.


ii) Dioptres


Explanation:1 dioptre is the power of a lens whose focal length is 1 metre. The power of a convex lens is positive and that of a concave lens is negative.


More from this chapter

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14

How can an AC generator be converted into a DC generator?

 15

Compute the position of the object placed in front of a concave mirror of focal length ‘f’ so that the image formed is of the same size of the object.

 2

Correct the mistakes, if any, in the following statements.

i) The magnetic field is a quantity that has magnitude only.


ii) Outside the bar magnet, the magnetic field lines emerge from the South Poleand merge at the North Pole.


 3

The ray diagram shown below is introduced to show how a concave mirror forms theimage of an object.


i) Identify the mistake and draw the correct ray diagram.


ii) Write the justifications for your corrections.