3. a) Two wires, A and B, are made of the same metal and have equai length, but the resistance of wire A is four times the resis- tance of wire B. How do their diameters compare? b) A wire of resistance R is stretched uniformly (keeping its volume constant) until it is twice its original length. What happens to the resistance?

3. a) Two wires, A and B, are made of the same metal and have equai length, but the resistance of wire A is four times the resis- tance of wire B. How do their diameters compare? b) A wire of resistance R is stretched uniformly (keeping its volume constant) until it is twice its original length. What happens to the resistance?