Current Intensity
Compute average current from I = Q/t, with reverse solutions for charge Q and time t.
Inputs
Formula
I = Q / t; Q = I·t; t = Q/I
Fundamentals
Current (current intensity) is charge passing a cross-section per unit time — a basic circuit quantity.
$I=Q/t$, $Q$ charge (C), $t$ time (s). In steady DC current is equal everywhere; with voltage/resistance $I=U/R$.
History
The ampere is defined from the magnetic force of current (1948); the force law traces to Oersted (1820) and Ampere.
Engineering applications
Used to set rated currents for conductors, fuses and contactors.
Glossary
| Current $I$ | Charge flow rate, ampere A. |
| Charge $Q$ | Basic quantity, coulomb C. |
| Time $t$ | Time for charge to pass (s). |
How to use
- Fill in Charge Q, Time t, Current I in the Inputs section (watch the unit on each field).
- Click Calculate; the tool evaluates the formula shown above.
- Read Current I, Charge Q, Time t in the results area.
Formula notesCurrent I = Q/t (Q charge, t time); or I = P/U.
Formula · Worked Example · Knowledge
Formula
Average current $I=Q/t$; reverse for charge $Q=It$ and time $t=Q/I$.
Worked Example
Q=10 C, t=5 s → I=2 A; with I=3 A → Q=15 C (t=5 s).
Key Points
- Current direction is defined by positive-charge flow.
- The ampere is an SI base unit.
- Conductor size relates to ampacity (see resistance).
Parameters
Inputs
| Parameter | Symbol | Unit | Default |
|---|---|---|---|
| Charge Q (C) | Q | C | 0 |
| Time t (s) | t | s | 5 |
| Current I (A) | I | A | 0 |
Outputs
| Result | Symbol | Unit |
|---|---|---|
| Current I | I | A |
| Charge Q | Q | C |
| Time t | t | s |
Applications
- Common engineering use cases
FAQ
What formula does this tool use?
This tool computes per ISO / AGMA / ASME standard formulas: I = Q / t; Q = I·t; t = Q/I
How accurate are the results?
Results match input precision, based on SI units and common engineering approximations; for critical duty re-check with a safety factor.
Where is it used?
Common engineering use cases