True Everywhere, Useful With Symmetry

You'll learnwhich currents count in Ampère's law, what the law can and cannot hand you, and why a current loop in a field twists instead of drifting.

Draw an imaginary loop around a wire and total up the magnetic field along one lap. The answer depends only on the current passing through the loop, even with a second wire sitting right outside it. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · WHAT IS ENCLOSED · SYMMETRY OR NOTHING · TORQUE NOT FORCE · v2

only enclosed current sets the lap · symmetry unlocks B · loops twist

Before you start

What you're looking at

A wire seen end on (the circled dot), with a dashed pink loop drawn around it. The loop is an imaginary path, not a wire.

The question

What does walking that loop and totalling the field tell you?

Step 1 / 12