Goal: Reason regarding forces between current elements
Source: 283-660 Force between two wires
A very long wire lies in a plane with a short wire segment. The long
wire carries current I, while the short wire of length L carries current
i. The two wires are parallel to each other. Which of the following
statements are true?

- The direction of the magnetic force
exerted by the long wire on the short wire is directed away from the
long wire.- The magnitude of the force on the short wire is
μ0IiL/2πd.- The long wire experiences a force
of exactly the same magnitude as the force experienced by the short
wire.
- A only
- B only
- C only
- A and B
- A and C
- B and C
- A, B, and C
- None of them are true
Commentary:
Answer
(6) The force is attractive between the wires so statement A is false.
Students need to interpret the phrase ‘very long’ as implying that the
wire is infinite.