Let denote the dimensional formula of the permittivity of the vacuum, and that of the permeability of the vacuum. If , , and ,
Answers: B. · C.
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Written solution
Step 1: Identify the given quantities and their dimensions.
The fundamental dimensions are mass , length , time , and electric current .
Step 2: Determine the dimensional formula of .
Use Coulomb's law for the electrostatic force between two charges.
Rearrange the equation to express in terms of the other variables.
Express the dimensions of charge , force , and distance .
Substitute these dimensions into the expression for .
Step 3: Determine the dimensional formula of .
Use the formula for the magnetic force per unit length between two parallel current-carrying conductors.
Rearrange the equation to express .
Since and both represent length, their dimensions cancel out.
Substitute the dimensions of force and current.
Step 4: Verify the relationship using the speed of light.
The speed of light in vacuum is related to and by .
This matches the dimension of .
Answer: and