Question

2. A student says that the resistance of two wires of same length and same area of cross section is same. This statement is correct if (a) Both wires are of different materials (b) Both wires are made of same material and are at different temperature. (c) Both wires are made of same material and are at same temperature. (d) Both wires are made of different materials and are at the same temperature.

Answer 1

R = ρL / A
For same length (L) and area (A) resistance depends on ρ and temperature.

Hence given statement is correct if both are made up of same material and are at same temperature. Correct option is (C).

Answer 2

This statement is correct if both wires are made of same material and are at same temperature.

To properly understand this answer, we have to know more about resistance and the factors which affects the resistance.

Resistance and the factors which affect resistance :

• The resistance is a property of an electrical conductor due to which it opposes the flow of electrical current through it.
• The resistance of a conductor depends upon - length of the conductor, area of cross section of the conductor, type of material of the conductor (resistivity) and temperature. (i.e. R = ρL/A)

Now, it is given that the two conductors have already the same length and cross sectional area. Which means, they have to be made out of same type of material (having same resistivity) and they have to stay in equal temperature, to have equal resistance.

Hence, the given statement is correct if both wires are made of same material and are at same temperature.

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