Electric field force calculator
A 2 microcoulomb charge in a 5000 N/C field feels 0.01 N. Enter charge and field with their signs, and the force comes out in newtons, pointing with the field for a positive charge and against it for a negative one. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Electric charge
- 0.000002
- Electric field strength
- 5,000
- Charge
- 0.000002
- Electric field
- 5,000
- Field
- 5,000
- F
- 0.01
An electric field force calculator multiplies charge by electric field strength to give the force that field exerts on the charge. Positive and negative charges reverse force direction along the same field axis, so signed scalars matter as much as magnitude.
What F = qE means for a charge in a uniform field
In classical electrostatics, a uniform electric field E exerts a force F equals q E on a point charge q. When q and E are expressed in SI units—coulombs for charge and newtons per coulomb or volts per meter for field—the product F is in newtons. Direction follows the product of signs along a chosen axis: a positive charge feels a force in the direction of E, while a negative charge feels a force opposite to E.
Zero charge or zero field yields zero force, which is physically valid and is not treated as an error by this tool. The model assumes a uniform field over the charge location, or at least a local field value you already know; it does not integrate non-uniform maps, solve Poisson’s equation, or compute E from distant sources.
Teachers and automated graders care about signed arithmetic and unit consistency as much as the multiply itself: students who mix microcoulombs with raw numbers without conversion will get a number that is off by powers of ten, and a silent unit conversion would hide that mistake. The check path recomputes q times E with the same fixed rounding used for published fields, so a successful response always ships with steps you can assert in tests or worksheets.
Prefer SI throughout: convert millicoulombs, nanocoulombs, and kilovolts per meter before calling so the product is already in newtons.
Practical tips, limits, and related searches
Keep charge and field inside the published absolute range so their product cannot overflow into a non-finite force that the solver must reject. Convert microcoulombs and kilovolts per meter to base SI before you call if you want F in newtons without mental rescaling afterward. Prefer this capability when you already have scalar q and E and only need F; if your source is a word problem about two point charges, first find E or use a Coulomb force tool.
Round-trip checks are easy: recompute q times E by hand and confirm it equals the published force within the same twelve-decimal rounding, and confirm that flipping the sign of q or E flips the sign of F while preserving magnitude.
What you can do with it
Homework checks for F = qE
Students enter charge and field from textbook problems and compare hand-written force magnitude and sign against a deterministic result before submitting.
Lab pre-flight for electrostatic setups
Technicians estimate force on a charged sample in a known uniform plate field before adjusting voltage or electrode spacing.
FAQ
What is the force on a charge in an electric field?
For a point charge q in a uniform electric field E, the force is F = q E. In SI units, q in coulombs and E in N/C (or V/m) give F in newtons.
Does the sign of the charge matter?
Yes. Positive q feels a force in the direction of E; negative q feels a force opposite to E. This tool returns a signed scalar along your chosen axis.
Does this solve Coulomb’s law for two charges?
No. It multiplies a given charge by a given field strength. Use a two-charge Coulomb tool if you need force from q1, q2, and separation.
Is the electric field force calculator free?
The browser tool is free and runs locally.
Why do I have to convert microcoulombs before entering them?
Because the calculator does not convert units: it multiplies exactly what you enter. With coulombs and newtons per coulomb the force comes out in newtons; for example, 2 microcoulombs is 0.000002 C.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/elec/electric-field-force \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"q":0.000002,"E":5000}'const res = await fetch("https://api.kit.forhosting.com/elec/electric-field-force", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"q": 0.000002,
"E": 5000
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/electric-field-force",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"q": 0.000002,
"E": 5000
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/electric-field-force", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"q":0.000002,"E":5000}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"q":0.000002,"E":5000}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/electric-field-force", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"q": 0.000002,
"E": 5000
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.electric_field_force",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Non-numeric, missing, or out-of-range inputs fail with invalid_input instead of inventing a force.
What F = qE means for a charge in a uniform field
The formula is the local definition of field strength for a test charge: E is the force per unit charge, so rearranging gives F equals q E.
How to call the API and what comes back
Prefer sending numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern including optional scientific notation. Send a JSON body with two required finite numbers: q (aliases charge and Q) for electric charge in coulombs, and E (aliases electric_field, field, and field_strength) for electric field strength in newtons per coulomb or volts per meter. Absolute values must stay within the published limit of one trillion so intermediate products remain finite in IEEE double precision on the Worker and in the browser. On success the response echoes rounded q and charge, E, electric_field, and field, sets F and force to the same rounded product, formula to the string F equals q E, equation to a human-readable substitution line, unit_force to N, unit_charge to C, unit_field to N/C, message to a short English summary, and steps to an ordered array of given values, formula, substitution, direction note, and summary. Failed validation—missing fields, non-numeric strings, non-finite numbers, values outside absolute limits, or a non-finite product—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, limits, and related searches
When teaching, pair examples: two microcoulombs in a five-thousand-newton-per-coulomb field yields one hundredth of a newton; a negative charge reverses the force sign; zero field yields zero force; and a non-numeric string demonstrates the hard invalid_input path. This landing targets people searching for an electric field force calculator, F equals q E, or force on a charge in an electric field; it is not a Coulomb-law two-charge solver, not a Gauss-law field finder, and not a full vector-field visualizer. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately send bad strings.
Integration use cases
Unit tests for electromagnetism solvers
Generate known-good positive, negative, and zero-force cases plus deliberate non-numeric rejections for coding kata expected values.
Technical questions
What if q or E is zero?
Then F = 0. Zero force is a valid result and is not treated as invalid_input.