Question

By increasing the temperature the resistance of a conductor:
A) Increases
B) Decreases
C) Remains constant
D) Initially increases then decreases

Answer 1

Hint: In order to find the correct answer to the given question we need to know the criteria on which the resistance of a body depends. After that we need to compare the criteria with the given option and then finally we can conclude with the correct option.

Complete answer:
First of all let us find out about the resistance of a body.
The resistance of a body is the hindrance for the flow of free electrons. Already we know that the Ohm’s law gives a relation between current and voltage supplied to a body at constant physical conditions. If these conditions will change then there will be a change in current and voltage supply.
Now let us find how change in temperature affects the resistance of a body.
We know that there is a random motion between the free electrons in a body. When we increase the temperature, in that case the velocity of the electrons also increases. This will result in a faster movement of the electrons resulting in the increase in the number of collisions between the free electrons. Now the free electrons will face more difficulty to move and ultimately the resistance of the body will increase. Therefore, the increase in temperature will lead to an increase in the resistance of the body.

Hence, option (A), i.e. increases is the correct choice of the given question.

Note: We know that,$R = \rho \dfrac{l}{A}$.
R = resistance of the wire.
l = length of the wire.
A = cross-sectional area of the wire
$\rho $= resistivity of the wire
Clearly, we can notice that the resistance of a body depends on the length, area and the resistivity of the body. Also, different materials have different values of resistivity. We should not get confused with the value of resistance using Ohm’s law relation. According to Ohm’s law voltage is directly proportional to the current in a body. Mathematically, we write it as,$V = IR$. Here, the resistance is the ratio of voltage and current but it does not change with the current or voltage supply.