70 likes | 210 Views
Electrostatics and Electric Fields. Parts of an atom Nucleus (protons, neutrons) Electrons Protons are positive (+) Electrons are negative (-) The force that holds atoms together is the strong nuclear force. There are four fundamental forces in nature. 1. Gravitational
E N D
Electrostatics and Electric Fields Parts of an atom Nucleus (protons, neutrons) Electrons Protons are positive (+) Electrons are negative (-) The force that holds atoms together is the strong nuclear force.
There are four fundamental forces in nature. 1. Gravitational 2. Electromagnetic 3. Strong Nuclear 4. Weak Nuclear • Many items in nature are conserved- this means they cannot be destroyed. Mass, energy, momentum, and charge.
Charge (q or Q) measured in a unit called Coulombs (C). • The charge on an electron or proton is the same, 1.602 E-19 C. • Charges of like signs repel. • Charges of opposite signs attract. • Neutral atoms have equal numbers of protons and electrons. • Electrons are able to move from one place to another, protons are not.
Coulomb’s Law- The Force that exists between two charged particles depends on the amount of charge on each and the distance squared between them. • Fe = kq1q2/ r2 k = 9 E9 Nm2/C2 • F ~ qq If charges change, force changes the same way. • F~ 1/r2 If distance increases, force decreases. Ex: if r doubles, F=1/4 original force.
Charge Transfer • Charges can be transferred 3 ways • Conduction (Friction and Contact) • Induction (nearness of charged objects) • Polarization (temporary realignment)
Conductors- allow electrons to move freely, usually charge will sit on the surface. • Insulators- charges are more tightly bound. Even charge distribution. • Semiconductors- usually mixed with an alloy to turn an insulator into a conductor. • Superconductors- very low resistance to the flow of charge at certain temps. Can conduct electricity without heating.
Electric Fields • Electric Field- a region in space where an electric force can be detected. • E = Fe/q E = kq/r2 Unit: N/C • Electric Field and Electrostatic Force are vectors, the direction matters! • Electric Field lines are drawn from a positive toward a negative. + -