Question:medium

The dimensions of magnetic flux are identical to the dimensions of:

Show Hint

Whenever an exam problem asks for dimensional matches, always look for a direct historical law equation before breaking terms down into basic $[M][L][T][A]$ base dimensions. Equations like $e = \frac{\Delta \phi}{\Delta t}$ (Faraday's Law) or $V = L\frac{di}{dt}$ let you deduce correct unit combinations in under ten seconds!
Updated On: May 29, 2026
  • EMF $\times$ Time
  • Electric field $\times$ Velocity
  • Force/Current
  • Magnetic field $\times$ Current
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Understanding the Question:
This question belongs to units and dimensions in physics. We are asked to identify which physical expression has the same dimensions as magnetic flux.
We can solve this by either deriving the dimensions from base SI units or by using fundamental equations from electromagnetism.
Step 2: Key Formulas and Approach:
According to Faraday's Law of Electromagnetic Induction, the induced electromotive force ($\text{EMF}$, denoted as $e$) is equal to the rate of change of magnetic flux ($\phi_B$):
\[ e = -\frac{d\phi_B}{dt} \] Using this relationship, we can determine the dimensions of magnetic flux directly by multiplying the dimensions of $\text{EMF}$ by those of time.
Step 3: Detailed Explanation:

Analyze Faraday's Law: Writing Faraday's Law in terms of dimensional formulas:
\[ [\text{EMF}] = \frac{[\text{Magnetic Flux}]}{[\text{Time}]} \]
Isolate Magnetic Flux: Rearranging the equation to isolate magnetic flux:
\[ [\text{Magnetic Flux}] = [\text{EMF}] \times [\text{Time}] \] This matches Option (A) directly.

Verify with Dimensional Formulas: Let us write down the explicit dimensions for absolute verification.

Magnetic flux is given by $\phi_B = B \cdot A$. Since $F = q v B \implies B = \frac{F}{q v}$:
\[ [B] = \frac{[M L T^{-2}]}{[A T][L T^{-1}]} = [M T^{-2} A^{-1}] \] \[ [\phi_B] = [B][A] = [M T^{-2} A^{-1}][L^2] = [M L^2 T^{-2} A^{-1}] \]
Electromotive force ($\text{EMF}$) is work done per unit charge:
\[ [\text{EMF}] = \frac{[M L^2 T^{-2}]}{[A T]} = [M L^2 T^{-3} A^{-1}] \]
Multiplying $\text{EMF}$ by time ($[T]$):
\[ [\text{EMF} \times \text{Time}] = [M L^2 T^{-3} A^{-1}][T] = [M L^2 T^{-2} A^{-1}] \]
The dimensions match exactly, confirming the relationship.

Step 4: Final Answer:
The dimensions of magnetic flux are identical to those of $\text{EMF} \times \text{Time}$, which corresponds to Option (A).
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