Key relationship
F⃗=q(E⃗+v⃗×B⃗); r=mv⊥/(|q|B).
Physics · Class 12
Lorentz force and circular motion
Only velocity perpendicular to B contributes to magnetic force. Parallel velocity gives no magnetic force. The magnetic-only circular radius is shown separately from the chosen electric force.
Open the interactive experiment →Lorentz force and circular motion
காந்தவிசை qvB sinθ. வேகம் காந்தப்புலத்திற்கு இணையாக இருந்தால் விசை பூஜ்யம்.
Key notes, relationships and model limits
Remember
Only velocity perpendicular to B contributes to magnetic force. Parallel velocity gives no magnetic force. The magnetic-only circular radius is shown separately from the chosen electric force.
Common trap
A magnetic force is perpendicular to velocity and does no work. The parallel velocity component does not set the gyration radius.
Model limits
Nonrelativistic particle. Electric force is chosen along the measured magnetic-force component. Radius applies to magnetic-only motion; zero B/q returns zero as a no-circle indicator.
What you will learn
Use the controls and plotted relation to explain lorentz force and circular motion.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
At q=1 nC, v=10 km/s and B=10 mT perpendicular to v, magnetic force is 10⁻⁷ N.
Why this matters
The model connects lorentz force and circular motion with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
A particle moving parallel to uniform B experiences magnetic force?
- qvB, its maximum value.
- Zero.
- A force in the direction of B.
Read the explanation
Zero.
Course connection: Class XII Chapter 4. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.