JEE MAIN - Physics (2011 - No. 10)
If a wire is stretched to make it $$0.1\% $$ longer, its resistance will:
increase by $$0.2\% $$
decrease by $$0.2\% $$
decrease by $$0.05\% $$
increase by $$0.05\% $$
Forklaring
Resistance of wire
$$R = {{\rho l} \over A} = {{\rho {l^2}} \over C}$$ (where $$Al=C$$ )
$$\therefore$$ Fractional charge in resistance
$${{\Delta R} \over R} = 2{{\Delta l} \over l}$$
$$\therefore$$ Resistance will increase by $$0.2\% $$
$$R = {{\rho l} \over A} = {{\rho {l^2}} \over C}$$ (where $$Al=C$$ )
$$\therefore$$ Fractional charge in resistance
$${{\Delta R} \over R} = 2{{\Delta l} \over l}$$
$$\therefore$$ Resistance will increase by $$0.2\% $$