JEE Physics Important Formulas Part -8

Lenz’s law formula

The formula for Lenz’s law are as stated below

Description

Formula

Magnetic Flux

The magnetic flux through a plane of area dA placed in a uniform magnetic field B is given as

ϕ=B∙dA

When the surface is closed, then magnetic flux will be zero. This is due to magnetic lines of force are closed lines and free magnetic poles is not exist

Lenz’s Law

The direction of induced emf or current in the circuit is in such a way that it opposes the cause due to which it is produced. Therefore,

E = -N(dϕ/dt)

Induced emf   

Induced emf is given as

  
E = -N(dϕ/dt)

E = -N((ϕ_1- ϕ_2)/t)

Induced Current   

Induced Current is given as

I=E/R = N/R(dϕ/dt)= N/R((ϕ_1- ϕ_2)/t)

Self – Induction

Change in the strength of flow of current is opposed by a characteristic of a coil is known as self-inductance. 

It is given as ϕ=LI

Here, L = coefficient of self – inductance

Magnetic flux rate of change in the coil is given as 

dϕ/dt = L dl/dt=-E

Mutual – Induction

Mutual – Induction is given as 

e_2=(d(N_2 ϕ_2)/dt = M (dl_1)/dt

Therefore,

M=(μ_0 N_1 N_2 A)/l