When a tuning fork, struck by a rubber pad, is held over a length of air column in a tube, it produces a loud sound for a fixed length of the air column.

i) Name the above phenomenon.

ii) How does the frequency of the loud sound compare with that of the tuning fork?

An object is placed infront of a convex lens such that the image formed has the same size as that of the object. Draw a ray diagram to illustrate this. 

Give two reasons as to why copper is preferred over other metals for making calorimeters. 

Calculate the amount of heat released when 5.0 g of water at 20^o C is changed into ice at 0^o C.

i) Define specific latent heat of vaporization of a substance.

Explain why water is used in hot water bottles for fermentation and also as a universal coolant. 

17.

A wire of uniform thickness with a resistance of 27 ohm is cut into three equal pieces and they are joined in parallel. Find the resistance of the parallel combination. 

Mention two factors on which the resistance of a wire depends upon? 

Draw a labelled diagram of a three-pin socket.

Find the cost of operating an electric toaster for two hours if it draws 8 A current on a 110 Volt circuit. The cost of electrical energy is Rs. 2.50 per kWh.