Key relationship
p=qℓ; Er=2kp cosθ/r³; Eθ=kp sinθ/r³; τ=pE sinθ.
Physics · Class 12
Electric dipole field and torque
Compare axial and equatorial fields and rotate a dipole in a uniform external field. The field falls as r⁻³ in the far-field approximation.
Open the interactive experiment →Electric dipole field and torque
இருமுனையின் திருப்புவிசை pE sinθ. அச்சுப் புலம் நடுக்கோட்டுப் புலத்தின் இருமடங்கு.
Key notes, relationships and model limits
Remember
Compare axial and equatorial fields and rotate a dipole in a uniform external field. The field falls as r⁻³ in the far-field approximation.
Common trap
The dipole moment points from negative to positive charge. The displayed far-field approximation requires distance large compared with separation.
Model limits
Far field r ≫ charge separation (controls enforce at least 5 times); uniform external E.
What you will learn
Use the controls and plotted relation to explain electric dipole field 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 p=2×10⁻⁸ C m and E=1000 V/m, the maximum torque is 2×10⁻⁵ N m.
Why this matters
The model connects electric dipole field 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
Where is dipole torque greatest?
- At 0°, where the dipole is aligned.
- At 90° to the uniform field.
- At 180°, where energy is greatest.
Read the explanation
At 90° to the uniform field.
Course connection: Class XII Chapter 1. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.