Question

1. A wire of resistance 8 Ohm stretched to twice its original length the resistance of stretched wire would be
(a) 32 ohm (b) 16 ohm (c) 8 ohm (d) none of these
​

Answer 1

Answer:

Correct option is B)

Let length and cross-section area of the wire be l and A respectively.

∴ Resistance R=ρ

A

l

where ρ is the resistivity of the material

Given : R=4 Ω

For l

′

=2l and A

′

=

2

A

, resistance of the wire be R

′

∴ R

′

=ρ

A

′

l

′

=ρ

A/2

2l

=4ρ

A

l

=4R

∴ R

′

=4×4 Ω=16 Ω