Post on 03-Jan-2016
Electric Forces and FieldsElectric Forces and FieldsHolt Physics: 17-1 Electric Charge Holt Physics: 17-1 Electric Charge
(Pages 628-633)(Pages 628-633)
2 Kinds of Electric Charge 2 Kinds of Electric Charge
Both were named by Ben FranklinBoth were named by Ben Franklin
1. Positive charge (+)1. Positive charge (+)
2. Negative Charge (-)2. Negative Charge (-)
Like charges repelLike charges repel
Opposite charges attractOpposite charges attract
Electric charge is conserved Electric charge is conserved
Electrons are transferred from one object to Electrons are transferred from one object to another when they come into contactanother when they come into contact
One object becomes negatively chargedOne object becomes negatively charged
One object becomes positively chargedOne object becomes positively charged
*** No charge is created or destroyed *** No charge is created or destroyed
The overall charge remains the sameThe overall charge remains the same
Electric charge is quantized Electric charge is quantized
Millikan’s oil droplet experimentMillikan’s oil droplet experiment Electric charge is measured in Coulombs (C) Electric charge is measured in Coulombs (C)
and is symbolized by “e”and is symbolized by “e” Quantized = occurs in discrete amountsQuantized = occurs in discrete amounts
++e , e , ++2e , 2e , ++3e , etc.3e , etc.
* Electrons have a charge of – e* Electrons have a charge of – e* Protons have a charge of +e* Protons have a charge of +e
* 1e = 1.60 x 10* 1e = 1.60 x 10-19-19 C C
Transfer of electric charge Transfer of electric charge
The speed of transfer depends on materialThe speed of transfer depends on material
Conductor Conductor - Material in which electric charge - Material in which electric charge moves freelymoves freely
Most metals are good conductorsMost metals are good conductors
Insulators Insulators - Material in which electric charge - Material in which electric charge doesn’t move freelydoesn’t move freely
Glass, plastic, wood, and rubberGlass, plastic, wood, and rubber
Transfer of electric chargeTransfer of electric charge
Semiconductors Semiconductors - Materials with properties - Materials with properties between conductors and insulatorsbetween conductors and insulators
Specific atoms have been added to Specific atoms have been added to
alter the properties alter the properties
Superconductors Superconductors - Become perfect - Become perfect conductors at or below at certain conductors at or below at certain temperatures.temperatures.
Insulators and conductors can be Insulators and conductors can be charged by contact charged by contact
Charged by contact by rubbing 2 insulators Charged by contact by rubbing 2 insulators together and they attract each other together and they attract each other
Conductors charged by induction Conductors charged by induction
Process of charging a conductor by Process of charging a conductor by placing it near a charged object then placing it near a charged object then grounding the conductor. (Fig 17-4) grounding the conductor. (Fig 17-4)
Requires no contact between objectsRequires no contact between objects
Conductors charged by induction Conductors charged by induction
GroundingGrounding- when a conductor is connected to - when a conductor is connected to the earth by a wire or copper pipe.the earth by a wire or copper pipe.
Surface charge is Surface charge is polarizationpolarization
An insulator is placed near a charged object.An insulator is placed near a charged object.
Electrons in the insulator align themselves to Electrons in the insulator align themselves to
the charged object (all positive’s on one side,the charged object (all positive’s on one side,
all negative’s on the other side)all negative’s on the other side)