Explain why, the current that makes the heater element very hot, only slightly warms the connecting wires leading to the heater.

Explain, why should the current be not passed through potentiometer wire for long time ?

(a) what is menat by the heating effect of current ? State three factors on which the heat produced in a wire by an electric current depends. (b) Explain why, through the heating element of an electric heater glows, but its connecting cord does not l glow. ( c) An electric geyser of resistance 20 Omega takes a current of 5 A. calculate the heat produced in 2 minutes. (d) Name the commercial unit of electric energy. How many joules are equal to this unit ?

The element of heater is very hot while the wires carrying current are cold. Why?

Statement I : The wires supplying current to an electric heater are not heated appreciably. Statement II: Resistance of connecting wires is very small and H prop R .

Explain why, it is difficult to hold a stainless steel tumbler containing very hot tea in the hand but a thermocol cup containing the same hot tea can be held easily.

When a circuit element X is connected across on a.c. source of e.m.f. 220 sqrt2 volt, current of sqrt2 A flows through it in phase with the voltage. When another element Y is connected across the same a.c. source, the same current flows through the circuit, but it leads the voltage by pi//2 radian. Name the circuit element X and Y. Find the current that flows in the circuit when series combination of X and Y is connected across the same source.

An ideal monatomic gas is confined in a cylinder by a spring-loaded piston of cross-section 8.0xx10^-3m^2 . Initially the gas is at 300K and occupies a volume of 2.4xx10^-3m^3 and the spring is in its relaxed (unstretched, unompressed) state, fig. The gas is heated by a small electric heater until the piston moves out slowly by 0.1m. Calculate the final temperature of the gas and the heat supplied (in joules) by the heater. The force constant of the spring is 8000 N//m , atmospheric pressure is 1.0xx10^5 Nm^-2 . The cylinder and the piston are thermally insulated. The piston is massless and there is no friction between the piston and the cylinder. Neglect heat loss through lead wires of the heater. The heat capacity of the heater coil is negligible. Assume the spring to be massless.