EasyPhysicsHigh School (9–10)Electricity & Magnetism › Electromagnetic InductionConceptualBoard Exam
A coil is joined to a galvanometer. Say whether a current is induced, and which way, in each case…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A coil is joined to a galvanometer. Say whether a current is induced, and which way, in each case.
- A magnet is pushed into the coil.
- The magnet rests inside the coil.
- The magnet is pulled out of the coil.
- The magnet is held still, and the coil is moved toward it.
- The coil and the magnet are carried along together, side by side.
Need a reminder? The key ideaShow
A current is induced in a coil while the magnetic field through it changes: when a magnet and the coil move relative to each other. It is larger for faster motion, a stronger magnet and more turns; it reverses when the motion reverses, and it opposes the change (Lenz's law). Fleming's right-hand rule: thumb for the motion, forefinger for the field, middle finger for the induced current.
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.
Step 1. (a) Yes: the field through the coil grows.
Step 2. (b) No: nothing changes, however strong the magnet.
Step 3. (c) Yes, the other way to (a): the field shrinks.
Step 4. (d) Yes, the same way as (a): only the relative motion matters.
Step 5. (e) No: the magnet does not move relative to the coil, so the field through it does not change.
Answer: (a) yes. (b) no. (c) yes, reversed. (d) yes. (e) no.
Check. In every "yes", the coil and the magnet move toward or away from each other.
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