The electric field lines extend away native a confident chargeThey move forward a an unfavorable charge

Let"s take it parallel plates, which make a uniform electrical field.If we take the basic learning, which i mentioned, in accounts, it"s an extremely easy to recognize that this is the direction of a optimistic charge thing if we put the object between the key (move far the positive charged plate and also toward negatively fee plate).

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The trouble is if we placed a an unfavorable charged thing between. Isn"t the electrical field reversed ?



The direction that the field is defined to it is in the direction the the pressure on a positively charged test particle. Hopeful charges always move far from various other +ve charges and also towards -ve charges.

Charlie says, that is a convention, favor driving top top the right (or left), or which pen on a plug is "live". So the everyone can agree ~ above the result of a calculation, us all have to define it the same way. It might be identified the other method round, but it isn"t. And we can"t have actually both - that would certainly be confusing.


The electrostatic field is a smart method to job-related with the Coulomb"s law. We know that a fee $Q$ located in $P$ will develop a pressure $ extbfF_e = fracQq^3 extbfPM$ on a charge $q$ situated in $M$. However, this expression the $ extbfF_e$ is not very convenient when you occupational with a continuous distribution that charges, that"s why we prefer to work with what we contact the electrostatic field, no an ext than a mathematical thing which facilitate the maths behind We define the electrostatic field created by the charge $Q(P)$ together the field $ extbfE(M)$ that, when multiplied by $q$, offers the pressure of the fee $Q$ on a charge $q$ located in $M$, ie. $$ extbfE(M) = fracQ^3 extbfPM$$

Using this definition of the electrostatic field, us can notification that it always goes away from positive charges, and also toward an unfavorable charges.

A ar line is characterized as a line the is always tangent to the field, and also is oriented by the field. Since the electrostatic ar is always directed far from optimistic charges and also toward an unfavorable charges, ar lines should go far from positive charges and toward negative ones.

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However, we can"t speak that ar lines space oriented by the motion of any charged object: indeed, together you sharp out, the electromagnetic pressure acting top top a charge $q$ depends on the signe of $q$ since this force is $ extbfF = q extbfE$. The electrostatic field doesn"t change, that is only the electrostatic force that is reversed by instead of a hopeful charge by a negative one.