Write an expression for calculating electrical power in terms of current and resistance

(a) Define Electric power. An electrial device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance. (b) Tow electric bulbs rated 100W , 220V and 60W, 220V are connected in parallel to an electric mains of 220V . Find the current draw by the bulbs form the mains.

Write an expression for the electrical power spent in flow of current through a conductor in terms of resistance and potential difference

Write an expression for the electrical energy spent in the flow of current through an electrical appliances in terms of I, R and t.

Electrical power P is given by the expression P = (Q xx V) div time. Express the power P in terms of current and resistance explaining the meaning of symbols used there in.

Define the following and write expressions for calculating each of them. Entropy of fusion

What is meant by dispersive power ? Write an expression of dispersive power in terms of refractive indices.

Define the following and write expressions for calculating each of them. Entropy of vapourisation.

(a) Define the term 'conductivity' of a metallic wire. Write its SI unit. (b) Using the concept of free electrons in a conductor, derive the expression for the conductivity of a wire in te'rms of number density and relaxation time. Hence obtain the relation between current density and the applied electric field E.

Write an expression connecting the resistance of a wire and specific resistance of its material. State the meaning of the symbols used.

Define the following and write expressions for calculating each of them. Entropy of sublimation.