Electric Fields
A field is the force per unit charge at a point.
About this topic
An electric field is the region around a charge where other charges feel a force. Field strength is E = F/q, in N/C, and field lines point in the direction a positive test charge would move: away from positive charges and toward negative. The denser the lines, the stronger the field.
A point charge produces E = kQ/r², and parallel charged plates give a uniform field E = V/d. For example, two plates 2 cm apart with 100 V between them have a field of 5000 V/m, and an electron in that field feels a constant force, much like a ball in gravity, so it follows a parabolic path.
Fields explain action at a distance, and how photocopiers, ink-jet printers and lightning work. They also guide the beam in old cathode ray tubes and the particles in accelerators.
Remember that field lines never cross, because the field has one direction at each point, and that the lines are a drawing aid, not physical threads. A charge does not feel its own field, only the field made by other charges.
Key ideas
- E = F/q
- Field lines point away from positives
- Closer lines mean stronger field
Quick check
Use cases: where Electric Fields helps
- Homework: review the key idea behind Electric Fields before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Electric Fields without notes.
- Visual learning: play with the interactive lab to see how Electric Fields changes when you adjust its inputs.
- Teaching a friend: explain Electric Fields in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Electric Fields?
A field is the force per unit charge at a point.
What will I learn in Electric Fields?
E = F/q. Field lines point away from positives. Closer lines mean stronger field.
Is Electric Fields part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Electric Fields lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Electric Fields?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.