Enter the field strength, power density, and the impedance of free space into the calculator to determine the missing variable.
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Field Strength to Power Density Formula
The following formula is used to calculate the power density for a given field strength and impedance of free space.
S = (E²) / (2 * Z)
Variables:
- S is the power density (W/m²)
- E is the field strength (V/m)
- Z is the impedance of free space (Ω)
To calculate the power density, square the field strength and divide by twice the impedance of free space.
| Field Strength (V/m) | Power Density (W/m²) |
|---|---|
| 1 | 0.001 |
| 2 | 0.005 |
| 3 | 0.012 |
| 5 | 0.033 |
| 10 | 0.133 |
| 20 | 0.531 |
| 27.5 | 1.003 |
| 30 | 1.194 |
| 38.8 | 1.997 |
| 50 | 3.316 |
| 61.4 | 5.000 |
| 75 | 7.462 |
| 100 | 13.263 |
| 137 | 24.893 |
| 150 | 29.841 |
| 200 | 53.050 |
| 300 | 119.363 |
| 400 | 212.202 |
| 500 | 331.565 |
| 1000 | 1326.260 |
| Uses free-space plane-wave relation: S = E² / (2·Z0). With Z0 = 377 Ω, S in W/m² when E is in V/m. | |
What is Field Strength?
Field strength, also known as electric field strength, is a measure of the force exerted by an electric field on a charged particle. It is typically measured in volts per meter (V/m). Field strength is an important parameter in electromagnetics and is used to describe the intensity of an electric field at a particular point in space. It plays a crucial role in the transmission and reception of electromagnetic waves, such as radio waves, and is a key factor in determining the power density of the field.
How to Calculate Field Strength to Power Density?
The following steps outline how to calculate the power density from field strength and impedance of free space.
- First, determine the field strength (E) in volts per meter (V/m).
- Next, determine the impedance of free space (Z) in ohms (Ω). The standard value is 377 Ω.
- Next, calculate the power density (S) using the formula S = (E²) / (2 * Z).
- Finally, calculate the power density.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Field Strength (E) = 50 V/m
Impedance of Free Space (Z) = 377 Ω