EasyPhysicsHigh School (9–10)Electricity & Magnetism › Magnetic Effects of CurrentConceptualBoard Exam
A magnetic field points from the top of the page to the bottom…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A magnetic field points from the top of the page to the bottom. Use Fleming's left-hand rule.
- A wire carries a current to the right. Which way is the force on it?
- What if the current goes to the left?
Need a reminder? The key ideaShow
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.
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) Forefinger down the page, middle finger to the right: the thumb points into the page.
Step 2. (b) The current is reversed, so the force is reversed: out of the page.
Answer: (a) into the page. (b) out of the page.
Check. The force is at right angles to both the field and the current, so it must be into or out of the page.
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