Key relationship
F = k q₁q₂/r².
Physics · Class 12
Coulomb force
Change signs to switch attraction and repulsion. Increase separation to see the force decrease with the square of distance. Positive force here means repulsion.
Open the interactive experiment →Coulomb force
மின்னூட்டங்களின் குறியீடுகள் ஈர்ப்பு அல்லது விலக்கலை தீர்மானிக்கின்றன. தூரம் இரட்டிப்பானால் விசை நான்கில் ஒன்று.
Key notes, relationships and model limits
Remember
Change signs to switch attraction and repulsion. Increase separation to see the force decrease with the square of distance. Positive force here means repulsion.
Common trap
Use centre-to-centre separation for the point-charge model; doubling r makes the force magnitude one quarter.
Model limits
Stationary point charges in vacuum, nonzero separation; positive radial force means repulsion.
What you will learn
Use the controls and plotted relation to explain coulomb force.
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 q₁=2 µC, q₂=3 µC and r=1 m, F≈0.0539 N; at 2 m it is ≈0.0135 N.
Why this matters
The model connects coulomb force with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
What happens when separation doubles?
- It becomes one half.
- The force magnitude becomes one quarter.
- It becomes four times larger.
Read the explanation
The force magnitude becomes one quarter.
Course connection: Class XII Chapter 1. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.