Question

In which situation will the lowest resistance occur? A. thick wire and high temperature B. thin wire and high temperature C. thick wire and cold temperature D. thin wire and low temperature

Answer 1

Answer:

C. thick wire and cold temperature

Explanation:

The resistance of a wire is given by:

$R=\rho \frac{L}{A}$

where $\rho$ is the resistivity of the material, L is the length of the wire, A is the cross-sectional area of the wire.

From the formula, we see that the thicker the wire, the larger A, therefore the smaller the resistivity: so, a thick wire will have lower resistivity.

Moreover, the resistance of a wire increases with the temperature: in fact, high temperatures mean more motion of the atoms/electrons inside the wire, so more resistance to the flow of current through it. Therefore, colder temperature means lower resistance.

So, the correct option is

C. thick wire and cold temperature

Answer 2

Answer:

A. thick wire and low temperature

Explanation:

The resistance of wire increases with increase in temperature because as temperature increases the electrons in the wire vibrates with more energy. These electrons creates obstacle for the moving electrons. Thus, resistance of wire increases with increase in temperature of the wire.

The formula for resistance of wire is given by,

$R=\frac{d l}{A}$

Where R = resistance of wire

d = density of wire

A area of cross section of wire

l = length of wire

Thus, resistance of wire is inversely proportional to the area of cross section of wire.

So, the resistance of wire is less for thin wire.

Hence, Answer is A. thick wire and low temperature.