Correct Answer - Option 3 : Vat = QρL

The correct answer is **Vat = QρL.**

**Formulae:**

Formula or equation used to find electrical resistivity(ρ) =\(\ RA\over L\)

\(R= {\rho L \over A} \longrightarrow\)①

The equation used to find charge (Q) = \(Current(i) \times Time(t) \)

\(i={Q\over t}\longrightarrow\)②

From ohm's Law:

\(V=iR\)

\(R={V \over i} \longrightarrow\)③

**Calculation:**

Substitute equation ③ in equation ①:

\({V \over i}={\rho L \over A}\longrightarrow\)④

Substitute equation② in equation ④:

\({Vt \over Q}={\rho L \over A}\)

Rearranging the above equation as:

**VAt = QρL.**

The Relation between** potential difference** ‘V’ across a metal wire of **resistivity** ‘ρ’,** length **‘L’, and** area of cross-section** ‘A’ through which a** charge **‘Q’ flows in ‘t’** seconds** is:

**VAt = QρL.**