Radius, r' = 2r
Area of cross-section, A'=πr'2=π(2r)2=4πr2=4A
The area of cross-section will increase by four times.
Then the new resistance,R'=ρlA'
Thus, the resistance will get reduced by four times.
When the diameter of wire is doubled its resistance befcomes: (a) Double (b) four times (c) one - half (d) one - fourth
The length of a simple pendulum is made one-fourth. Its time period becomes :
(a) four times (b) one-fourth
(c) double (d) half.
Keeping the p.d. constant, the resistance of the circuit is halved. The current will become. (a) One-fourth (b) four times (c) half (d) double