When a potential difference of 10 v is placed across a certain solid cylindrical resistor, the current through it is 3 a. if the diameter of this resistor is now tripled, the current will be: a) 2/9 a b) 2/3 a c) 27 a d) 18 a.

C) 27 A

Explanation:

ΔV = Potential difference across the cylindrical resistor = 10 V

i = current through the resistor = 3 A

R = Resistance of the resistor

Using ohm's law

ΔV = i R

10 = 3 R

R = 3.33 ohm

The resistance of a resistor is inversely related to square of the diameter. So as the diameter is tripled, the resistance becomes 1/9 times

R' = New resistance of the resistor  =

i' = new current through the resistor

Using ohm's law

ΔV = i' R'

i' = 27 A