Deduce the relation J → = σ E → from first principles considering Ohm's law to be true.

From Ohm's law-Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. I = V R J = I A = V R A = E I ρ L A A = E ρ = σ E Current density J is a vector quantity which is defined as the current flowing per unit area measured in a direction normal to the direction of flow of charge. The vector J is parallel to the electric field vector.

Show that current density J → = n e 2 τ m E → ?

electrons move with an average velocity which is independent of time, although electrons are accelerated. This is the phenomenon of drift and the velocity v d is called the drift velocity. v d = e E m τ i ∆ t = n e A v d ∆ t i = n e 2 E A m τ j → = i A = c u r r e n t d e n s i t y J → = n e 2 E m τ where ; j =current density A = Area of cross-sectional m =mass of electron e =electron E = electric field τ = Relation time

E M B I B E

Bureau's Higher Secondary Physics Class 12>Chapter 5 - Electric Current>MODEL QUESTIONS

Odisha Board Solutions for Chapter: Electric Current, Exercise 1: MODEL QUESTIONS

Author:Odisha Board

Odisha Board Physics Solutions for Exercise - Odisha Board Solutions for Chapter: Electric Current, Exercise 1: MODEL QUESTIONS

Attempt the free practice questions on Chapter 5: Electric Current, Exercise 1: MODEL QUESTIONS with hints and solutions to strengthen your understanding. Bureau's Higher Secondary Physics Class 12 solutions are prepared by Experienced Embibe Experts.