Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A wire long carries in a field of . Find the force on it when it lies (a) along the field, (b) at to the field, (c) at right angles to the field.
A wire with a current in a magnetic field feels a force , where is the angle between the wire and the field. It is largest () at right angles, and zero along the field. Fleming's left-hand rule: forefinger for the field, middle finger for the current, thumb for the force.
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. The largest force. .
Step 2. (a) Along the field, : .
Step 3. (b) .
Step 4. (c) .
Answer: , and .
Check. The force grows as the wire turns away from the field, and is largest at right angles.
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