Electromagnetism
Electric Field Calculator
Calculate electric field strength E = kq/r² from a point charge. Solve for field, charge or distance.
Result
E = kq/r²
Step-by-Step Solution
What is an Electric Field?
An electric field is a region around a charged particle where another charge experiences a force. The electric field strength E at a point is defined as the force per unit positive test charge placed at that point. Point charges create fields that diminish with the inverse square of distance.
E = kq/r²
k = 8.9875×10⁹ N·m²/C² | q = source charge (C) | r = distance (m) | E = field strength (N/C or V/m)
💡 Electric field lines always point from positive to negative charges and never cross each other. The density of field lines indicates field strength — closely packed lines mean a stronger field.
Real-World Applications
Capacitors
Parallel plate capacitors store energy in the uniform electric field between the plates.
CRT Screens
Cathode ray tubes use electric fields to deflect an electron beam and draw images on the screen.
Lightning
Thundercloud charge separation creates enormous electric fields that ionise air, triggering lightning.
Gel Electrophoresis
DNA and protein molecules migrate through gel under an applied electric field, separating by size.
Frequently Asked Questions
What is the difference between electric field and electric force?
Electric field E = F/q (force per unit charge) is a property of the space around a charge. Electric force F = qE depends on the test charge. The field exists independently of whether there is a test charge present.
What are the units of electric field?
N/C (Newtons per Coulomb) or equivalently V/m (Volts per metre). These are the same: 1 N/C = 1 V/m. The V/m form is more common in engineering.
How does the electric field vary with distance?
For a point charge, E ∝ 1/r² (inverse square law). Doubling the distance reduces the field to one quarter. For an infinite line charge, E ∝ 1/r. For an infinite plane of charge, E is constant regardless of distance.