Using the model
Symbols, assumptions and limitations
This point-charge model assumes a stationary isolated source in vacuum and sets potential to zero at infinity. Electric field is a vector directed away from a positive source and toward a negative source; electric potential is a signed scalar.
Worked examples
See the method in practice
Positive microcoulomb source
At 0.500 m from +2 µC, the field is about 71,900.414 N/C and the potential is about 35,950.207 V.
Negative source
The field magnitude is unchanged for −2 µC, but the potential becomes negative and the field points toward the source.
Questions
Frequently asked
How do field and potential differ?
Electric field is force per unit positive test charge and has direction. Potential is energy per unit charge and is a scalar.
Why does E decrease faster than V?
For a point charge, field follows 1/r² while potential follows 1/r.
Does the test charge affect these results?
No. E and V describe the source charge at the selected position; a sufficiently small test charge is assumed not to disturb it.
Sources & review
Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.
OpenStax University Physics — Electric Field OpenStax University Physics — Electric PotentialWritten by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology