104 g of water at 30°C is taken in a calorimeter made of copper of mass 42 g. When a certain mass of ice at 0°C is added to it, the final steady temperature of the mixture after the ice has melted, was found to be 10°C. Find the mass of ice added.
[Specific heat capacity of water = 4.2 J g^-1 °C^-1; Specific latent heat of fusion of ice = 336 J g^-1; Specific heat capacity of copper = 0.4 J g^-1 °C^-1 ]

The melting point of naphthalene is 80°C and the room temperature is 30°C. A sample of liquid naphthalene at 100°C is cooled down to the room temperature. Draw a temperature time graph to represent this cooling. In the graph, mark the region which corresponds to the freezing process.

(i) Define nuclear fission.

(ii) Rewrite and complete the following nuclear reaction by filling in the atomic number of Ba and mass number of Kr :

${}_{92}^{235}\text{U}${92}^{235}\text{U} + ${0}^{1}\text{n}$ ⟶ ${}_{\mathrm{.}\mathrm{.}\mathrm{.}}^{144}\text{Ba}${…}^{144}\text{Ba} + ${36}^{…}\text{Kr}$ + 3 $_{0}^{1}\text{n}$ + Energy

The diagram below shows a magnetic needle kept just below the conductor AB which is kept in North South direction.

(i) In which direction does the needle deflect when the key is closed ?

(ii) Why is the deflection produced?

(iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB ?

(iv) Name one device which works on this principle.