Light – Reflection and Refraction — Science STD 10 — Question

Explain why the planets do not twinkle but the stars twinkle.

How does the resistance of an ohmic conductor depend on the applied voltage?

Describe how fossil fuels were formed.

Which kind of mirror is used in the headlights of a car? Why is it used for this purpose?

The energy in petrol originally came from the sun. Explain how it got into petrol.

a. Write the mathematical expression for Joule's law of heating.
b. Compute the heat generated while transferring 96000 coulomb of charge in two hours through a potential difference of 40 V .

Why does a driver prefer to use a convex mirror as a rear-view mirror in a vehicle?

Describe with a suitable diagram, how a convex mirror diverges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of convex mirror in this diagram.

In the straight wire A, current is flowing in the vertically downwards direction whereas in wire B the current is flowing in the vertically upward direction. What is the direction of magnetic field:

1. In wire A?
2. In wire B?

Name the rule which you have used to get the answer.

Calculate the resistance of an electric bulb which allows a 10 A current when connected to a 220 V power source?