Final answer:
When two wires of the same size are parallel, the breaking force will be 2F. If a single wire has double the diameter, its breaking force will be F.
Step-by-step explanation:
The breaking force for a wire depends on its size and properties. Let's answer each part of the question:
(a) When two wires of the same size are parallel, the breaking force will be 2F. This is because the forces on both wires will be equal in magnitude and in opposite directions, resulting in a total force of 2F.
(b) If a single wire has double the diameter, its breaking force will be F. This is because the breaking force is determined by the cross-sectional area of the wire, and doubling the diameter results in four times the area, but only half the force per unit area, giving the same breaking force of F.