Magnetic Force on Charges and Wires
A magnetic field pushes moving charges sideways.
About this topic
A magnetic field exerts a force on moving charges: F = qvB sin θ, perpendicular to both the velocity and field, so it changes direction but not speed, bending charges into circles. On a current-carrying wire, F = BIL sin θ. Fleming's left-hand rule gives the direction.
For example, a 2 m wire carrying 5 A at right angles to a 0.1 T field feels a force of 0.1 × 5 × 2 = 1 N. A charged particle moving in a circle has radius r = mv/qB, so faster or heavier particles curve more gently, which is how mass spectrometers separate ions.
This force turns electric motors, steers electron beams in old TVs, and curves particle paths in accelerators and mass spectrometers. It also shields Earth, as the magnetic field deflects charged particles from the Sun.
A key point is that the magnetic force does no work on a moving charge, since it acts at right angles to the motion, and a stationary charge feels no magnetic force at all. Be careful with the left-hand rule: first finger field, second finger current, thumb motion.
Key ideas
- F = qvB sin θ
- Left-hand rule for motors
- The force does no work
Quick check
Use cases: where Magnetic Force on Charges and Wires helps
- Homework: review the key idea behind Magnetic Force on Charges and Wires before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Magnetic Force on Charges and Wires without notes.
- Visual learning: play with the interactive lab to see how Magnetic Force on Charges and Wires changes when you adjust its inputs.
- Teaching a friend: explain Magnetic Force on Charges and Wires in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Magnetic Force on Charges and Wires?
A magnetic field pushes moving charges sideways.
What will I learn in Magnetic Force on Charges and Wires?
F = qvB sin θ. Left-hand rule for motors. The force does no work.
Is Magnetic Force on Charges and Wires part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Magnetic Force on Charges and Wires lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Magnetic Force on Charges and Wires?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.