If a wire is stretched to make it 0.1% longer, its resistance will:
A.
increase by 0.2%
B.
decrease by 0.2%
C.
decrease by 0.05%
D.
increase by 0.05%
Answer :
increase by 0.2%
Solution :
Resistance of wire
$$R = \frac{{\rho l}}{A} = \frac{{\rho {l^2}}}{C}\left( {{\text{where}}\,Al = C} \right)$$
∴ Fractional change in resistance
$$\frac{{\Delta R}}{R} = 2\frac{{\Delta l}}{l}$$
∴ Resistance will increase by 0.2%
Releted MCQ Question on Electrostatics and Magnetism >> Electric Current
Releted Question 1
The temperature coefficient of resistance of a wire is 0.00125 per $$^ \circ C$$ At $$300\,K,$$ its resistance is $$1\,ohm.$$ This resistance of the wire will be $$2\,ohm$$ at.
The electrostatic field due to a point charge depends on the distance $$r$$ as $$\frac{1}{{{r^2}}}.$$ Indicate which of the following quantities shows same dependence on $$r.$$
A.
Intensity of light from a point source.
B.
Electrostatic potential due to a point charge.
C.
Electrostatic potential at a distance r from the centre of a charged metallic sphere. Given $$r$$ < radius of the sphere.