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A square loop of wire, of side a, lies midway between two
Chapter 7, Problem 23P(choose chapter or problem)
Problem 23P
A square loop of wire, of side a, lies midway between two long wires, 3a apart, and in the same plane. (Actually, the long wires are sides of a large rectangular loop, but the short ends are so far away that they can be neglected.) A clockwise current I in the square loop is gradually increasing: d I/dt = k (a constant). Find the emf induced in the big loop. Which way will the induced current flow?
Questions & Answers
QUESTION:
Problem 23P
A square loop of wire, of side a, lies midway between two long wires, 3a apart, and in the same plane. (Actually, the long wires are sides of a large rectangular loop, but the short ends are so far away that they can be neglected.) A clockwise current I in the square loop is gradually increasing: d I/dt = k (a constant). Find the emf induced in the big loop. Which way will the induced current flow?
ANSWER:
Step 1 of 3
Instead of finding the flux through the big loop due to the current in the small one, find the flux through the small one due to the large one, same current I flowing through it. The magnetic field of the big loop is just the field of two infinite wires, one at 
Both contributions point downwards.
