How much has a filament diameter decreased due to evaporation if the mainteenance of the previous temperature required an increase of voltage by `eta=1.0%`. The amount of heat transferred from the filament to surrounding space is assumed to be proportional to the filament surface area.

A metal ball of mass 1.0 kg is kept in a room at 15^(@)C . It is heated using a heater. The heater supplies heat to the ball at a constant rate of 24 W. The temperature of the ball rises as shown in the graph. Assume that the rate of heat loss from the surface of the ball to the surrounding is proportional to the temperature difference between the ball and the surrounding. Calculate the rate of heat loss from the ball when it was at temperature of 20^(@)C .

An incandesent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current The hot filament emits black-body radiation The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evapo ration of operation due to non-uniform evapo ration of ungsten from the filament If the buld is powered at constant voltage which of the following statement (s) is (are) ture ? .

An incandesent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current The hot filament emits black-body radiation The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evapo ration of operation due to non-uniform evapo ration of ungsten from the filament If the bulb is powered at constant voltage which of the following statement (s) is (are) true ? .

Indian style of cooling drinking water is to keep it in a pitcher having porous walls. Water comes to the outer surface very slowly and evaporates .Most of the energy needed for evaporation is taken from the water itself and the water is cooled down. Assume that a pitcher contains 10kg water and 0.2g of water comes out per second. Assuming no backward heat transfer from the atmosphere to the water, calculate the time in which the temperature decreases by 5^(@)C . Specific heat capacity of water = 4200J kg^(-1).^@C^(-1) and latent heat of vaporization of water = 2.27 xx 10^(6)J kg^(-1)

A truck of mass M has 4 wheels. The surface area of the metal disc in each wheel is A. When brakes are applied the brake shoe in each wheel rubs against the metal disc. This produces heat. We will assume that this heat is used to heat the disc in the wheel only. Each disc has mass m and is made of material of specific heat capacity s. One day the truck was going downhill on a road inclined at angle theta to the horizontal. To maintain a constant speed v the driver had to apply brakes. The only other dissipative force, apart from the brake force, on the truck is the air resistance force that is equal to F. Assume no heating of discs due to air friction. (a) Find the initial rate of rise of temperature of each metal disc after the brakes are applied. (b) Find the final temperature (T) of the disc assuming that it is a black body and it loses heat only through radia- tion. Take the atmospheric temperature to be T_(0)