Question

Which of the following quantities do not change when an ohmic resistor connected to a battery is heated due to the current?

• A. drift speed
• B. resistivity
• C. resistance
• D. number of free electrons

Answer 1

Answer: (D)

number of free electrons

We know, for a conductor carrying current,
Drift speed $=neI=ne\frac{V}{R}$
Resistivity $=\frac{RA}{L}$
where,
$n$ is no. of electrons,
$e$ is charge on electrons,
$V$ is applied voltage,
$R$ is resistance and
$A$ and $L$ are area of cross-section and length of resistor.
From above equations it is clear that drift speed, resistivityand resistance of resistor will be affected due to heating of resistor