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Physics · Class 12

Charge and dipole potential energy

Potential & Capacitance

Choose a point-charge pair or a dipole in an external field. Pair energy kq₁q₂/r can be positive or negative. Dipole energy −pE cosθ is lowest when aligned with the field.

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Charge and dipole potential energy

புள்ளி மின்னூட்ட ஜோடிக்கு ஆற்றல் kq₁q₂/r. ஒரே குறிக்கு நேர்மறை; எதிர்குறிக்கு எதிர்மறை. இருமுனையின் ஆற்றல் −pE cosθ; புலத்துடன் ஒரே திசையில் குறைந்தது.

Key notes, relationships and model limits

Key relationship

Upair=kq₁q₂/r; Udipole=−pE cosθ.

Remember

Choose a point-charge pair or a dipole in an external field. Pair energy kq₁q₂/r can be positive or negative. Dipole energy −pE cosθ is lowest when aligned with the field.

Common trap

Potential energy belongs to an interacting system. Its sign depends on the stated zero and on the charge signs or dipole orientation.

Model limits

Choose either two stationary point charges in vacuum, with pair energy zero at infinite separation, or an ideal dipole in a prescribed uniform electric field.

What you will learn

Use the controls and plotted relation to explain charge and dipole potential energy.

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 pE=2×10⁻⁵ J, U is −2×10⁻⁵ J at 0° and +2×10⁻⁵ J at 180°.

Why this matters

The model connects charge and dipole potential energy with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

Which dipole orientation has minimum potential energy?

Read the explanation

Aligned with the field at 0°.

Course connection: Class XII Chapter 2. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.