1. Two wires - A and B - with circular cross-sections have identical lengths and are made of the same material. Yet, wire A has four times the resistance of wire B. How many times greater is the diameter of wire B than wire A?

Diameter of wire B is 2 times the diameter of wire A

Explanation:

We have given two wire A and B

They are made up of same material and length of both the wire is sane

So

Let the resistivity of both the wire is

It is given that wire A has 4 times the resistance as wire B

So

So ( As )

So diameter of wire B is 2 times the diameter of wire A

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6