Presentation on theme: "Electrostatics Deals with electric charges at rest, or static electricity on the surface of an object."— Presentation transcript:
1ElectrostaticsDeals with electric charges at rest, or static electricity on the surface of an object.
2Sub-atomic particles Effect static electricity charging Protons (p+) in nucleus (center) of an atompositively chargedNeutrons (n0)neutral (no effect on charge)Electrons (e-)move freely outside of the atomnegatively charged
3RULE OF ELECTRIC CHARGE Electrical Charge – a force that one charge exerts on anotherAn amount of static electricity can ignite volatile substances (gasoline)A large difference in the charges in the air can trigger a lightning.Opposite charges attract each otherprotons are attracted to electrons because they have different electric chargesLike charges repelone electron would repel another electron because they have the same electric charge.
4Mobility of charged particles Remember, an electron (e-) is free to move but a proton is “locked in” to the nucleus of an atom. This means that when charging occurs, the electrons either move from one physical body to another, OR are rearranged within an existing body. DON’T FORGET THIS!
5Migrant Electrons Electrons are opportunistic migrants for electrons to make a move from the atoms of one material to the atoms of another material, there must be an energy source, a motive, and a low-resistance pathway.Charged objects (ions) have an unequal number of protons and electrons
6Unit of ChargeCoulombThe charge on a single electron is -1.6 x CThe charge on a single proton is +1.6 x CCharge is the difference between number of electrons and protons
7Example 1 – Calculating Charge The amount of charge carried by a lightning bolt is estimated at 10 C. What quantity of excess electrons is carried by the lightning bolt?1 electron = 1.6 x C(10 C)(1.6 x C) = x 1019electrons
8Electric Charge is Conserved When one body loses an electron, the other body will gain that electron so that there is a net charge on each body, but no electrons are destroyed in the process.
9How distance effects strength of attraction – Coulomb’s Law The farther apart opposite charges are, the weaker the attraction force between them.The closer the charges get, the stronger the force becomes.F = forcekc = Coulomb’s constant (9x109 Nm2/C2 )q1 = charge of particle 1q2 = charge of particle 2r = distance
10Example 2 – Coulomb’s Law One charge of 2.0 C is 1.5 m away from a – 3.0 C charge. Determine the force they exert on each other.The negative sign just means that one charge is positive, the other is negative, so there is an attractive force between them.
11Example 3Two balloons are charged with an identical quantity and type of charge of -6.25x109 C. They are held apart at a separation distance of .617 m. Determine the magnitude of the electrical force of repulsion between them.
12Example 4Two balloons with charges of μC and μC attract each other with a force of Newton. Determine the separation distance between the two balloons.
13Insulators Any material that does not conduct electricity store electrons on their surface.Ex: Plastics, dried wood, glass, fabric, and other non-metalsMetals are CONDUCTORS, and do not store charges (wires in your home, etc.)
18InductionWhen a charged object approaches, but does not touch an uncharged object, a migration of electrons creates an “apparent” charge on the object even though the net charge remains zero
19Charging by Induction: Charged object drives off like charges, leaves charged object with opposite charge
20Electric FieldField Lines -Invisible lines surrounding a charge manifesting a force.Number of lines per area represents field strengthAs lines diverge, field strength diminishesMore charges means greater number of field lines
21Electric FieldField lines move away from positive toward negative charges.
22Example 5 Which region experiences greater electric field strength? region AWhere is that region located?near the charge
23Electric Dipole Two point charges of equal magnitudes and opposite signs.Near the charge the field lines are radialAll lines that emerge will terminateEmerge on positive charge and terminate on negative.
242 Equal Positive Charges Field lines do not crossRepulsionLike ChargesFor Negative charges, reverse the direction of the field lines.
25Unequal ChargesGiven a positive charge that is 2X that of negative, how will the lines terminate?Only half the lines that emanate from the positive charge will terminate in negative chargeRest of lines terminate at infinity.