Electric Field Calculator
Point charge or parallel plates, in N/C and V/m.
Work out Electric Field. Point charge or parallel plates, in N/C and V/m. Written for the problem set you are stuck on.
Charge in coulombs for a point charge, voltage in volts for plates.
Optional — gives the force a charge placed there would feel.
Electric field strength
8.9876e+5 N/C
Point charge — field falls as 1/r²
N/C and V/m are the same unit written two ways, which is worth knowing because the two halves of a course use different ones without saying they are equivalent. A point charge's field falls as 1/r², so it drops fast. Between parallel plates it is uniform — the same everywhere in the gap — which is why capacitors and CRT deflection plates are built that way and why E = V/d is so much simpler than the point-charge form. Air breaks down at about 3 × 10⁶ V/m, which sets the practical ceiling for any of this in atmosphere. Past that you get a spark rather than a field.
How the Electric Field Calculator works
Get field strength from a point charge or between parallel plates, with the force on any test charge you place there. N/C and V/m are the same unit written two ways, which the page states because different halves of a course use different ones.
Also known as: electric field strength calculator · e = v/d calculator · field of a point charge · electric field between plates
Frequently asked questions
How do I calculate electric field strength?
For a point charge, E = kq/r². Between parallel plates, E = V/d — much simpler, because the field there is uniform.
Are N/C and V/m the same thing?
Yes, exactly. A newton per coulomb and a volt per metre are dimensionally identical, and which one gets used is a matter of whether the discussion is about force or about potential.
Why is the field between parallel plates uniform?
Because the plates are large compared with their separation, so the contributions spread out evenly. That uniformity is why capacitors and deflection plates are built this way.
How strong a field can air withstand?
About 3 × 10⁶ V/m. Beyond that air ionises and you get a spark instead of a field, which sets the practical ceiling for high-voltage work in atmosphere.
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