Energy Density Units Electromagnetic Waves

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SUMMARY

Energy density in electromagnetic waves is measured in Joules per cubic meter (J/m³). This unit quantifies the amount of energy stored in a given volume of space. The discussion clarifies that while the electric field (E) and magnetic field (B) are related through the equation E = cB, the concept of energy density specifically pertains to the energy contained within a unit volume, analogous to mass density. Understanding this distinction is crucial for grasping the principles of electromagnetic theory.

PREREQUISITES
  • Understanding of electromagnetic wave theory
  • Familiarity with Maxwell's equations
  • Knowledge of units of measurement in physics
  • Basic concepts of energy density and mass density
NEXT STEPS
  • Study Maxwell's equations in detail
  • Explore the relationship between electric and magnetic fields in electromagnetic waves
  • Learn about energy density calculations in various physical contexts
  • Investigate the implications of energy density in practical applications, such as telecommunications
USEFUL FOR

Students of physics, educators teaching electromagnetic theory, and professionals in fields related to telecommunications and energy management will benefit from this discussion.

PeachBanana
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Homework Statement



In what units is energy density measured?

1. Watts
2. Watts per cubic meter
3. Newtons per meter
4. Joules per cubic meter

Homework Equations



E = cB (as derived by Maxwell)

The Attempt at a Solution



This question is so basic yet I'm confused. I thought "B" (magnetic field) had units of Tesla. I thought "c" (speed of light) had units of m/s. I was thinking the answer was Tm / s. I'm particularly confused as to where "per cubic meter" comes into play.
 
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E = cB (as derived by Maxwell)

This relates the magnitude of the electric field and the magnetic field in a plane wave.

The left side is electric field (not energy).
PeachBanana said:

Homework Statement



In what units is energy density measured?

1. Watts
2. Watts per cubic meter
3. Newtons per meter
4. Joules per cubic meter

I'm particularly confused as to where "per cubic meter" comes into play.

You don't have to appeal to energy density of EM fields to answer this question. Think of what does 'energy density' mean? Mass density (or just density for short) tells how much mass there is in a unit volume and is measured in kg/m3. So energy density means...
 
Hi.

Thank you. I like the way you explained it - made it much easier to understand.
 

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