Question

A piece of wire of rsistance 20ohm is drawn out so that its length is increased to twice its
original length. Calculate the resistance of the wire in the new situation.​

Answer 1

Explanation:

Given resistance = R1 = 20 ohm

Let length of the wire = L

Therefore, new length of the wire = 2L

Since, when the length is doubled, cross sectional area of the wire becomes half.

Therefore, new resistance = R = 2L/ (A/2) =4L/A

R = 4 x 20 (since, L/A = resistance)

R = 80 ohm.

hope you understood.

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Answer 2

Answer:

R=DL/A

Explanation:

IT BECOMES 20= DL/A.....1

LET NEW RESISTANCE BE X .. NOW X= D2L /A ... BUT WE KNOW THAT DL/A = 20 SO THE VALUE OF 2DL/A BECOMES 40