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What are the similarities and differences in magnetic and electric field?

Similarities and differences in magnetic and electric field (Dilpreet posted this question)

Similarities Differences
 Both electric and magnetic field are conservative forcesBoth obey inverse square law

Both are non contact forces (Forces can be exerted without contact)

Both are attractive as well as repulsive (Like poles repel, like charges repel; unlike poles attract, unlike charges attract)

 Electric field is produced by a charge whether at rest or in motionBut magnetic field is produced only by a moving charge


The total magnetic flux through any closed surface is always zero, but the total electric flux through any closed surface is equal to the net charge enclosed by the surface multiplied by the reciprocal of absolute permitivity

Electric field lines are discontinuous as they have a starting point (+ charge) and an ending point (- charge); But magnetic field lines are continuous, they always form closed loops


Electricfield, Magnetic Field and Photon

We know that photon has no charge. Then where from it gets electric and magnetic field in light?

Malik Sajad asks


Electric and magnetic fields are not produced by the photon; it is massless too.

But, photon is created by time varying electric and magnetic fields, usually produced by accelerated charges.

As you might have already learnt, a charge at rest produces an electric field around it. A moving charge (current) produces a magnetic field around it as well as magnetic field. A varying current produces a varying magnetic field and hence an induce emf or current. An accelerated charge produces a time varying electric and magnetic fields.

Thus under suitable situations, the electric and magnetic fields can reinforce each other and propagate out as pure electromagnetic form of energy and such a packet of energy is called photon.

Solution to HC Verma Problem

“Referring to HC Verma Part 2, chapter 29, Electric field and potential, Q 69
I think that Force is inversely proportional to square of the distance between the charged particles, so acceleration is not constant and hence
v*v  =  u*u  + 2*a*s   is not valid in this case.
How is proceed with this question ?” Satyam asked

How atoms are formed? – Neeraj Asks

Neeraj asks: ”We have read that atoms can neither been created nor been destroyed!
I want to know from where atoms came in existence,if they can not been created,also atom contain electron and proton which are negatively and positively charged,i want to know from where these charge came?”


Your question will be answered soon

Electrostatic induction – Where does the charge go on earthing?

Rajkumar asks:”in electrostatic induction in step 3 when earthed wire is removed then where the free negative charge go.does they go to earth then what happen to them.”

Waiting for responses from visitors

Mass of Proton

Anshul asks:

“how can we say that charge and mass of a proton has a constant value if it depends on the nature of the gas taken”

Answer: The mass of proton does not depend on the nature of gas or material.

Mass of a charged particle !

Monu asks:

“Can mass of a charged particle be infinite and if
yes explain how and when?????”


Answer: Please note that charge is independent of speed but mass depends on speed. So of a body of any mass is moving with gradually increasing speeds, its mass goes on increasing as per the theory of relativity (The relativistic mass ) but the charge remains the same.

Therefore, the mass of a charged particle can be infinity.

(If any of the visitors has got a different opinion, please post them as comments to this post.)

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