Key relationship
Baxial=2µ₀m/(4πr³); Bequatorial=µ₀m/(4πr³); τ=mB sinθ.
Physics · Class 12
Magnetic dipole fields and torque
Axial field magnitude is twice the equatorial magnitude at equal radius. A separate uniform external field rotates the magnet toward its minimum-energy alignment.
Open the interactive experiment →Magnetic dipole fields and torque
ஒரே தூரத்தில் அச்சுப் புலம் நடுக்கோட்டுப் புலத்தின் இருமடங்கு. காந்தம் வெளிப்புலத்தோடு சீராகத் திரும்பும்.
Key notes, relationships and model limits
Remember
Axial field magnitude is twice the equatorial magnitude at equal radius. A separate uniform external field rotates the magnet toward its minimum-energy alignment.
Common trap
Compare axial and equatorial fields at the same distance. Equal distance does not imply equal direction or magnitude.
Model limits
Far-field point dipole; angle control is used separately for probe polar angle and external-field orientation.
What you will learn
Use the controls and plotted relation to explain magnetic dipole fields and torque.
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
For m=1 A m² and external B=50 µT, maximum torque is 50 µN m.
Why this matters
The model connects magnetic dipole fields and torque with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
At equal radius the axial field magnitude is?
- Half the equatorial magnitude.
- Twice the equatorial magnitude.
- The same as the equatorial magnitude.
Read the explanation
Twice the equatorial magnitude.
Course connection: Class XII Chapter 5. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.