Definition and Discovery of Electrostatic Induction
– Electrostatic induction is a redistribution of electric charge in an object caused by nearby charges.
– It is also known as electrostatic influence or simply influence in Europe and Latin America.
– Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762.
– Electrostatic generators, such as the Wimshurst machine and the Van de Graaff generator, use this principle.
– The electrostatic potential (voltage) is constant at any point throughout a conductor due to induction.
Explanation of Electrostatic Induction
– A normal uncharged object has equal numbers of positive and negative electric charges in each part of it.
– In electrically conductive objects, such as metals, some of the electrons are able to move freely.
– When a charged object is brought near an uncharged, electrically conducting object, the internal charges separate.
– The electrons in the metal are attracted towards the charged object, leaving a region of negative charge.
– This results in induced charges on the object, with the polarity depending on the charge of the nearby object.
Charging an Object by Induction
– The induction effect can be used to put a net charge on an object.
– If an uncharged object is momentarily connected to electrical ground while near a positive charge, it gains a net negative charge.
– This method can be demonstrated using a gold-leaf electroscope.
– Induction causes a separation of charges inside the electroscope, resulting in the gold leaves spreading apart.
– By briefly grounding the electroscope, the charge on the object is neutralized, leaving a net charge on the electroscope.
The Electrostatic Field Inside a Conductive Object is Zero
– The electrostatic field of a nearby charge causes induced surface charges in metal objects.
– Negative charges are attracted and move to the surface facing the external charge, while positive charges are repelled.
– These induced surface charges create an opposing electric field that cancels the field of the external charge inside the metal object.
– The movement of charges is caused by the force exerted on them by the electric field of the external charge.
– An equilibrium is reached where the induced charges cancel the external electric field throughout the interior of the metal.
Reversibility of Electrostatic Induction
– The induction effect is reversible; if the nearby charge is removed, the induced charges intermingle again.
– The redistribution of charges during induction does not change the total charge on the object.
– When an object is grounded, the induced charges can flow into or out of the object.
– The sign of the charge left on an object after grounding is always opposite in sign to the external inducing charge.
– The two rules of induction are: equal and opposite charges are induced in the object when it is not grounded, and grounding a part of the object causes an opposite charge to be attracted from ground. Source: https://en.wikipedia.org/wiki/Electrostatic_induction
Electrostatic induction, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electric charge in an object that is caused by the influence of nearby charges. In the presence of a charged body, an insulated conductor develops a positive charge on one end and a negative charge on the other end. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the Van de Graaff generator and the electrophorus, use this principle. See also Stephen Gray in this context. Due to induction, the electrostatic potential (voltage) is constant at any point throughout a conductor. Electrostatic induction is also responsible for the attraction of light nonconductive objects, such as balloons, paper or styrofoam scraps, to static electric charges. Electrostatic induction laws apply in dynamic situations as far as the quasistatic approximation is valid.
