Download Electrostatics

Electrostatics
Electrical Forces and Charges
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All atoms held together by ____________________ forces
Electrical forces much stronger than _______________________ forces
Two types of electrical charge called ____________ and ___________________
Most materials have as much positive as negative charge and so are electrically ____________
Negative charge of ________________ exactly equal in magnitude to positive charge of ____________
Like charges __________; opposite charges _________________
Can be demonstrated with _______________ and charged rods
Conservation of Charge
If electrons are removed or added to a neutral atom, a net charge results; atom now is _____________
If electron(s) _________________, positive ion results
If electron(s) _________________, negative ion results
Outermost electrons often can be easily removed by __________________ with certain materials
Result is one object with ______________ charge (extra electrons) and one with _____________ charge (lost
electrons)
No charge created by this process, only ________________________ of charges
Charge is __________________, never created or destroyed
Quantization of Charge
No matter how much charge is assembled for any purpose, it’s always made up of ______________ and/or
____________________
___________________ amount of charge possible is that of one electron or proton
Charge is ________________: it comes in certain size small packages or _______________________
Charles Augustin de Coulomb
Coulomb’s Law
A law that relates the electrical force with the amount of ______________ and the ______________ between
the charges
Fundamentally identical to the law of ________________________________________
F = kq1q2/d 2
k is a ___________________ equal to 9.0 x 109 Nm2/C2
Fundamental unit of electric charge is the _________________ (C), a large amount of charge equal to that of
6.25 billion billion electrons
Like the law of gravitation, this is _______________________ law: changing the distance between the charges
changes the force by the square of the reciprocal of the distance change - triple d, get 1/9 F
_______________________ forces predominate with large objects because electrical forces cancel by equal
and opposite charges
Electrical forces control chemical ___________________ and the creation of compounds involving sharing or
taking of electrons
Conductors and Insulators
___________________: material through which electric charge can easily move - usually a _______________
because of loosely held electrons
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________________: material that inhibits the motion of charge - electrons are tightly bound to atoms
Extremely wide range of ___________________
Between insulators and conductors are ________________________ - materials like Si and Ge that are
normally insulators but can be made to conduct by the addition of certain impurities
At very cold temperatures, some materials become ________________________, with no resistance to charge
flow
Buildup of Static Charge
When contact is made between materials that attract electrons differently, electrons can be
___________________
One object becomes negatively charged, the other gets equal ___________________ charge
Often seen in daily life, such as socks in the dryer, a wool sweater, scuffing shoes on carpet
Charging by Conduction
When charged object makes _______________ with a conductor, electrons can flow into or out of the
conductor.
Leaves a charge of the ______________________ on the conductor after charged object is removed
Charging by Induction
Bringing charged object near a conductor will cause electrons to be __________________ on the conducting
surface
Negatively charge rod near metal sphere will cause electrons to move away from rod, inducing
________________ charge near rod
If second sphere touches first sphere, electrons will run onto it to get away from rod
If spheres are now _________________, one will remain positive other negative
Can also be charge sphere by induction if it is touched while charged rod is nearby, allowing path for charge
flow (_______________)
_________________ charge of rod remains on sphere
Same process occurs during _________________________; opposite charge is induced on earth by cloud
___________________ kite experiment proved this
Pointed objects allow charge to concentrate and leak off, preventing lightning strikes - lightning rod. invented
by _____________________
Charge Polarization
Insulators can also be charged by induction but results in _________________ of the molecules since electrons
can’t move freely
One side of atom or molecule becomes slightly ____________, other side slightly ____________________
Explains how bits of paper can be picked up by charged comb or balloon can stick to wall
Since opposite charges are closer together than like charges, ____________________ force results
Some molecules naturally polarized, like water; called ____________________________