Correct Answer - Option 1 : electromagnetic power density
Poynting vector:
It states that the cross product of electric field vector (E) and magnetic field vector (H) at any point is a measure of the rate of flow of electromagnetic energy per unit area at that point that is
\( \vec S = \vec E \times \vec H\)
S = Poynting vector
E = Electric field and
H = Magnetic field
The Poynting vector describes the magnitude and direction of the flow of energy in electromagnetic waves per unit volume.
∴ The dimensions of both the Poynting vector and the electromagnetic power density are the same, i.e. M1 L-1 T-2
M = Mass
L = Length
T = Time
Notes:
Current density:
- Denoted by J, the electric current density is the rate at which charge flows (electric current) per unit area of cross-section.
- It is a vector quantity since it has both magnitude and direction.
- Its magnitude is the current per unit area and its direction is the same as that of the charges at that point.
- Current per unit area (taken normal to the current), I/A, is called current density.
It is denoted by J.
- The SI units of the current density are A/m2 and dimension is given by M0L-2T0I1 or [M0 L−2 T−1 Q]
