Two long parallel wires are 7.5 cm apart…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two long parallel wires are cm apart. They carry A and A in the same direction. Find the force on each metre of either wire, and say whether it is an attraction or a repulsion. On the line between the wires, how far from the A wire is the field zero? Find the force on a m length of the A wire.
Need a reminder? The key ideaShow
Two long parallel wires, a distance apart, pull on each other with on each metre. The wires attract when the currents are in the same direction, and repel when they are opposite. The field of one wire is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. A, A, m.
Step 1. The force on each metre. , that is mN on each metre. The currents are in the same direction, so the wires attract.
Step 2. The quiet line. Between the wires, the field of wire 1 points one way and the field of wire 2 points the other way. They cancel at a distance from wire 1 when . So cm.
Step 3. The m length. mN.
Answer: mN on each metre, an attraction; cm from the A wire; and mN.
Check. The quiet line is nearer the wire with the smaller current, as it should be.
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