Question

2 points
A piece of wire of resistance 20 ohm is drawn so that its length is
increased to twice its original length. Calculate resistance of wire in new
situation. *
O
27 ohm
0
36 ohm
O
45 ohm
O
80 ohm​

Answer 1

Explanation:

Resistance is 20 ohm.

If Length increased twice then area will be halved AS IT is inversely proportional.

So new Resistance =?

Let length (original) be l.

And area is a.

So that time the Resistance was 20 ohm.

$20ohm = \frac{rho \times length}{area}$

Now new Resitance will be r .

$r = \frac{2 \times l \times rho}{ \frac{a}{2} }$

So , the equation will be

$r = 4 \times \frac{rho \times length}{area}$

$r = 4 \times 20$

r = 80 ohms is the new resistance.