Calculator Input
Formula Used
This calculator uses Coulomb’s law and vector addition. For each charge, the distance vector from the charge to point D is used.
r = √((xD − xi)² + (yD − yi)²)
Exi = kqi(xD − xi) / (εr × r³)
Eyi = kqi(yD − yi) / (εr × r³)
Ex = ΣExi, Ey = ΣEyi,
and |E| = √(Ex² + Ey²).
Electric potential is also estimated with
V = Σ(kqi / (εr × r)).
How to Use This Calculator
- Enter the x and y coordinates of point D.
- Select the distance unit used for every coordinate.
- Enter each source charge value and its unit.
- Enter the x and y location of each charge.
- Disable unused charges by clearing their checkbox.
- Enter relative permittivity. Use 1 for air or vacuum.
- Press the calculate button.
- Review the result, graph, CSV file, or PDF file.
Example Data Table
| Item | Charge | x | y | Unit | Use |
|---|---|---|---|---|---|
| Point A | 4 µC | 0 | 0 | m | Positive source charge |
| Point B | -2 µC | 3 | 0 | m | Negative source charge |
| Point C | 1.5 µC | 0 | 4 | m | Positive source charge |
| Point D | Field point | 1.5 | 1.5 | m | Target location |
Understanding Electric Field Magnitude at Point D
What the Result Means
Electric field strength describes force per unit positive test charge. At point D, the field may come from many nearby charges. Each charge creates its own field. The final answer is not a simple scalar sum. Direction matters. Positive charges push the test charge away. Negative charges pull it closer. This calculator resolves every contribution into x and y components. It then adds those components. The magnitude is found from the final vector.
Why Coordinates Matter
Coordinates define the distance and direction between charges and D. A closer charge usually has a stronger effect. Coulomb’s law follows an inverse square pattern. If distance doubles, field strength becomes one fourth. That makes location very important. Small coordinate changes can shift the final result. They can also change the angle strongly. The graph helps you see this behavior.
Using the Medium Setting
The relative permittivity setting adjusts the field for materials. Air and vacuum use a value near one. Water, glass, oil, and plastics use higher values. A higher value reduces the field. This is useful for practical study problems. It also helps when modeling dielectric materials. Always match this value with your textbook or lab data.
Advanced Checks
The component table shows each charge contribution. Use it to inspect signs and directions. A negative component does not mean a wrong answer. It means the vector points toward a negative axis. The potential value is also included. Potential is scalar, so it adds differently. Compare field and potential carefully. They answer different questions. Export the result when you need a record.
FAQs
1. What is point D in this calculator?
Point D is the target location where the electric field is measured. It is not treated as a source charge.
2. Can I use negative charges?
Yes. Enter a minus sign before the charge value. The calculator will reverse the direction of that field contribution.
3. What unit is used for the final field?
The final electric field is displayed in newtons per coulomb. This is equivalent to volts per meter.
4. Why does the calculator use vector components?
Electric fields have direction. Components allow fields from different charges to be added correctly before finding the final magnitude.
5. What should I enter for relative permittivity?
Use 1 for air or vacuum. For other materials, enter the dielectric constant given by your teacher, lab sheet, or reference table.
6. Why is the result very large?
Large values often happen when point D is very close to a charge. Coulomb’s law grows quickly as distance becomes small.
7. Can I disable unused charges?
Yes. Clear the checkbox beside any charge you do not want included in the net electric field calculation.
8. Is electric potential the same as electric field?
No. Electric field is a vector. Electric potential is a scalar. This calculator shows both for deeper comparison.