Question

Poynting Vector:

• A. points in the direction of electric field
• B. is given by \(\dfrac{1}{\mu_0}\left(\dfrac{\vec{E}\times\vec{B}}{2\epsilon_0}\right)\)
• C. is force-energy theorem of electrodynamics
• D. is work-energy theorem of electrodynamics and is given by \(\dfrac{1}{\mu_0}(\vec{E}\times\vec{B})\)

Hint:

Poynting vector is \(\vec{S}=\frac{1}{\mu_0}(\vec{E}\times\vec{B})\), and it gives the direction of electromagnetic energy flow.

Answer 1

The Correct Option is D

Concept:
Poynting vector represents the rate of electromagnetic energy flow per unit area.

Step 1: Formula of Poynting vector.
The Poynting vector is: \[ \vec{S}=\frac{1}{\mu_0}(\vec{E}\times\vec{B}) \]

Step 2: Direction of energy flow.
The direction of \(\vec{S}\) is perpendicular to both \(\vec{E}\) and \(\vec{B}\), not necessarily along the electric field.

Step 3: Meaning.
Poynting theorem represents conservation of electromagnetic energy and is often treated as the work-energy theorem of electrodynamics. \[ \therefore \text{Correct Answer is (D)} \]