Consider a resistor of uniform cross-sectional area connected to a battery of internal resistance zero. If the length of the resistor is doubled by stretching it, then

Options

A. the current will become four times
B. the electric field in the wire will become half
C. the thermal power produced by the resistor will become one fourth
D. The product of the current density and conductance will become half.

Answer

B, C

Explanation

b.,c.
(Moderates) As the length is doubled, the cross-sectional
area of the wire beocmes half, thus the resistance of the wire
`R = rhol//A` becomes four times the previous value. Hence after
the wire is elongated, the current becomes one-fouth. Electric field is potential difference per unit length and hence becomes
half the initial value. The power delivered to resistance is
`P = V^2//R` and hence becomes one-fourth.