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DFCCIL Executive S&T 2018 Official Paper

Option 1 : σ = J/E

CT 1: Current Affairs (Government Policies and Schemes)

54993

10 Questions
10 Marks
10 Mins

__Concept__:

V = R I

Where V is the potential difference, R is resistance and I is current flowing

Current density (J): The electric current per unit area is called current density.

\(Current~density~\left( J \right)=\frac{Current~\left( I \right)}{Area~\left( A \right)}\)

Conductivity (σ): The property of a conductor due to which the current flows through it is called the conductivity of that conductor.

\(Resistance~\left( R \right)=\frac{\rho ~l}{A}\)

Where ρ is resistivity = 1/σ, l is the length and A is the area of the conductor

Electric field (E) = potential difference (V)/length (l)

__Analysis__:

As, V = R I

\(Resistance~\left( R \right)=\frac{\rho ~l}{A}\)

\(V=\frac{\rho ~l}{A}\times I=\left( \frac{1}{σ } \right)\times l\times \frac{I}{A}=\left( \frac{1}{σ } \right)\times l\times J\)

\(J=σ \times \frac{V}{l}=σ ~E\)

σ = J/E