A physical quantity →S is defined as →S=(→E×→B)/μ0, where →E is electric field, →B is magnetic field and μ0 is the permeability of free space. The dimensions of →S are the same as the dimensions of which of the following quantity(ies) ?
A
Energycharge×current
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B
ForceLength×Time
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C
EnergyVolume
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D
PowerArea
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Solution
The correct option is DPowerArea →S=[→E×→B]μ0
Here, S is the Poynting vector which denotes flow of energy per unit area per unit time, which is energy flux or intensity.
∴→S=EnergyTime-Area or ForceTime- Length
So, unit of →S is Wattm2.
And here, options (B) and (D) have same unit, so these two are the correct options.