# Electro-Static Revision Notes

Essay by pulketHigh School, 12th grade February 2004

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*Electric Current is a flow of electric charges, consisting of electrons. Two types of charges - positive and negative. No charge matter is neutral. Forces between charges are called electrostatic forces. - Like charges repel, unlike attract.

*Rule - charge must always be conserved, it cannot be created or destroyed.

*Current measured with an ammeter, voltage measured with a voltmeter.

*Current (I) = Charge (Q) / Time (t)

*Coulomb (C) is amount of charge passing a point when a current of an ampere flows for a second.

*Electricity is conducted only through material soluble in water when in water, aqueous solutions and in a molten state.

*Material allowing flow of charge is a conductor otherwise an insulator.

*Instrument used to show the existence of a charged object is called a gold leaf electroscope, which moves in a certain direction depending on the charge on the object once the leaf has been charged and another charged object is brought near it.

*Two main processes for an object to gain charge, other than friction - charging by contact and by induction (charge separation).

*Coulomb's Law - Force (F) = (k.q1.q2) / r2

Coulomb's constant is k, q is charge and r is distance - if more than two charges use vector addition - find the resultant.

*Electric field is produced by a charge or a combination of charges. Forces are felt depending directly on the test charge placed in the field.

*Electric Field, E = F / q

E = q / 4 ÃÂ0 r2

*Comparison with gravity - Force felt by objects with charge - Force felt by objects with mass. Force proportional to size of charges - Force proportional to size of masses. Force inversely proportional to square of separation of charges - Force inversely proportional to square of separation...