In electrostatics we assume that the charges are held at rest and no magnetic fields are generated. But is it true that in electrostatics it is not necessary that charges are at rest ; rather current can flow but it should not vary with time and magnetic field can be created but it should be time independent or it may vary with time vary slowly ? Explain and justify.

Asked by Ankita Patel | 8th May, 2012, 09:24: PM

Expert Answer:

Electrostatics is a branch of sience where the eletrons, or the charged particles do not or slowly move.When certain types of materials are rubbed against other certain types, charge may be transferred from one to the other. 

Each object contains charge. For most objects, the number of negative charges equals the number of positive charges, giving a net charge of zero. These charges are free to move, however. When certain types of materials are rubbed against each other, the material's atoms are arranged such that some of the charges from one material will be transferred to the other material. This gives both objects a net charge. One object will be positively charged, the other will be negatively charged. For example, when a teflon rod is rubbed against silk, charge is transferred. When an uncharged object is placed near a charged object its charges rearrange themselves. Those charges attracted to the charged object move towards the charged object and those charges repelled move away. This effect is known as polarization. 

As discussed before, most objects are uncharged. An uncharged object means that the total number of positive charges equals the total number of negative charges. The net charge on the object is zero. When an uncharged object is polarized as described above, its net charge remains zero. No additional charge is put on the object. What does happen, however, is the charges inside the object rearrange themselves. When a negatively charged object, for instance, is placed near an uncharged object, the negative charges move away from the charged object and the positive charges move towards the charged object. It is this effect that makes the uncharged object act as if it is charged. 

Answered by  | 9th May, 2012, 09:58: AM

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