Question Details

ML³ T⁻¹Q² is dimension of

Options

A

Resistivity

B

Conductivity

C

Resistance

D

None of these

Correct Answer :

Resistivity

Solution :

The correct option is Resistivity .

Let's derive the dimensional formula step-by-step to identify the quantity that matches ML3T-1Q-2 (or ML3T-1Q2 depending on charge notation, let's analyze carefully with respect to charge Q).
Recall the relation between resistance R and resistivity ρ:
R=ρlA
where l is length and A is area. Thus, resistivity ρ is given by:
ρ=RAl

First, let's find the dimensions of resistance R using Ohm's Law (V=IR):
R=VI
Since potential difference V is work done (W) per unit charge (Q):
V=WQ
The dimensional formula of work W is [ML2T-2]. Therefore, the dimension of potential V in terms of charge Q is:
[V]=[ML2T-2][Q]=[ML2T-2Q-1]

Electric current I is rate of flow of charge:
I=QT
So, the dimension of current I is:
[I]=[QT-1]

Now, substituting the dimensions of V and I to find the dimensions of resistance R:
[R]=[ML2T-2Q-1][QT-1]=[ML2T-1Q-2]

Now we calculate the dimension of resistivity ρ:
[ρ]=[R]×[A][l]
Since area [A]=[L2] and length [l]=[L]:
[ρ]=[ML2T-1Q-2]×[L2][L]
[ρ]=[ML3T-1Q-2]

This matches the given dimensional formula (taking the standard notation where charge Q is represented). Hence, the quantity is Resistivity.

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