Define Young's modulus of elasticitiy. normal stress and longitudinal strain. Give unit of each of them. Derive an expression for the elastic potential energy of a wire, when stretched.

Define the term electric dipole moment. Give its units Derive an expression for the maximum torque acting on an electric dipole, when held in a uniform electric field.

Define electric potential difference between two points in an electric field and derive an expression for it. Also give S.I. unit of electric potential differnce.

Two wires of the same material and length but diameters in the ratio 1:2 are stretched by the same force. The potential energy per unit volume for the two wires when stretched will be radio.

A steel wire of mass mu per unit length with a circular cross section has a radius of 0.1 cm. The wire is of length 10 m when measured lying horizontal, and hangs from a hook on the wall. A mass of 25 kg is hung from the free end of the wire. Assuming the wire to be uniform and lateral strains < < longitudinal strains, find the extension in the length of the wire. The density of steel is 7860 kg m^-3 (Young's modulues Y = 2 xx 10^11 N m^-2)

A metallic wire is stretched by suspending a weight from it.If l is teh longitudinal strain and Y is the Young's Modulus,show that elastic potentially enrgy per unit volume is given by 1/2 Yl^2 .

A stell wire of length 4 m ,is stretched through 2 mm ,.The corss - sectional area of the wire is 2.0 mm^2 .If young's modulus of steel si 2.0 xx 10 ^11 N//^2 find The elastic potential energy stored in the wire.