🏫 Board🧲 Physics

Find the dimensions of \(\frac{B}{\mu_0}\) (Shift I Memory Based)

Q1 FREE PREVIEW

Find the dimensions of \(\frac{B}{\mu_0}\) (Shift I Memory Based)

a

[AL]

b

\(\left[{\mathrm{AL}}^{-1}\right]\)

c

[MAL]

d

\(\left[{\mathrm{MALT}}^{-1}\right]\)

✓ Correct answer: b)

\(\left[{\mathrm{AL}}^{-1}\right]\)

Explanation

Magnetic field B :
The dimensional formula for B is derived from the Lorentz force law:

\(
F=q v B \quad \Rightarrow \quad B=\frac{F}{q v}
\)

1. Force (F) has the dimensional formula:

\(
[F]=\left[\mathrm{MLT}^{-2}\right]
\)

2. Charge (q) has the dimensional formula:

\(
[q]=[\mathrm{AT}]
\)

3. Velocity (v) has the dimensional formula:

\(
[v]=\left[\mathrm{LT}^{-1}\right]
\)


Thus, the dimensional formula for B is:

\(
[B]=\frac{\left[\mathrm{MLT}^{-2}\right]}{[\mathrm{AT}]\left[\mathrm{LT}^{-1}\right]}=\frac{[\mathrm{M}]\left[\mathrm{T}^{-2}\right]}{[\mathrm{A}]}=[\mathrm{M}]\left[\mathrm{A}^{-1}\right]\left[\mathrm{T}^{-2}\right]
\)


Magnetic permeability ( \(\mu_0\) ):
The dimensional formula of \(\mu_0\) is:

\(
\left[\mu_0\right]=[\mathrm{M}][\mathrm{L}]\left[\mathrm{T}^{-2}\right]\left[\mathrm{A}^{-2}\right]
\)


Dimensions of \(\frac{B}{\mu_0}\) :
Using the formula:

\(
\frac{B}{\mu_0}=\frac{[\mathrm{M}]\left[\mathrm{A}^{-1}\right]\left[\mathrm{T}^{-2}\right]}{[\mathrm{M}][\mathrm{L}]\left[\mathrm{T}^{-2}\right]\left[\mathrm{A}^{-2}\right]}
\)


Cancel the terms:

\(
\frac{B}{\mu_0}=[\mathrm{A}]\left[\mathrm{L}^{-1}\right]
\)

Practice more Board Physics PYQs

See every question on Units and Measurements, or browse the full Board question bank.

See all questions on Units and Measurements →