Key relationship
E = kq/r²; Fprobe = qprobe E.
Physics · Class 12
Point-charge field and field lines
A positive test charge defines field direction. Positive sources have outward radial fields; negative sources have inward fields. The graph records that signed radial direction.
Open the interactive experiment →Point-charge field and field lines
நேர்மறை மின்னூட்டத்திலிருந்து புலக்கோடுகள் வெளியேறுகின்றன; எதிர்மறை மின்னூட்டத்தை நோக்கிச் செல்கின்றன.
Key notes, relationships and model limits
Remember
A positive test charge defines field direction. Positive sources have outward radial fields; negative sources have inward fields. The graph records that signed radial direction.
Common trap
The field is defined per unit positive test charge; reversing the probe charge reverses its force, not the source field.
Model limits
Point charge in vacuum; graph uses signed radial E. Field lines indicate direction and do not depict moving material.
What you will learn
Use the controls and plotted relation to explain point-charge field and field lines.
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
A +2 µC charge produces an outward field ≈17,975 N/C at 1 m.
Why this matters
The model connects point-charge field and field lines with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Which way does the field of a negative point charge point?
- Radially away from the negative charge.
- Radially toward the charge.
- Tangentially around the charge.
Read the explanation
Radially toward the charge.
Course connection: Class XII Chapter 1. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.