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# Tag Archives: resistivity

## Resistance and Resistivity

**Simran Asked**

“Two wires A and B of equal lengths,different cross-sectional areas and made of same metal a)name the property which is same for both the wires. b)name the property which is different for both the wires”

**Answer**:

Since both the wires are of same metal, the

resistivity will be samefor both whereas since the dimensions (Area of cross section here) are different, theresistance will be different

## Change in resistance due to stretching a wire

“There is a wire whose resistance is R. it is streched, and its length gets increased to 2%. find new resistance.” – Knishka Agrawal asked

Answer: The resistivity does not change due to stretching, but the length and area of cross section changes; but the volume remains constant. Therefore, resistance changes which can be calculated from the formula for Resistance

## Change in Resistance due to stretching a wire

Sreshtha asked:

“A piece of wire is redrawn without any change in volume so that its radius become half the original. Compare the new resistance with the original value.”

Answer:

When we redraw the wire, the volume remains constant and the resistivity also remains constant. SO, the variables are

- area of cross section and
- the length

When radius becomes half, the area of cross section increases in such a way that A1l1 = A2l2. This implies that when length is halved, area of cross section is doubled.

We know that

Therefore, the new resistance becomes (1/4) th the original value.

So, R2:R1 = 1:4