Presentation Transcript

1. Chapter 21 Physics

2. Electric charges Two types of Electric charge one called positive and the other negative. When charges are the same in an object it is neutral. An object can lose or gain an electric charge therefore it has a net charge
3. Charge stability Static electricity is a tiny imbalance of charges and can be transferred easily to help restore a zero charge. Structure of an atom need to know the charge in coulombs and the mass of the parts of an atom.
4. Parts of the atom Mass and charges Mass and charges Electron has a mass of 9.109 X 10-31 kg Electron has a charge of -1.602 X 10-19 C Proton has a mass of 1.673 x 10-27 kg Proton has a charge of + 1.602 X 10 -19 C Neutron has a mass of 1.675 X 10-27 kg Neutron has a charge of 0
5. Coulomb was named in honor of Charles Coulomb who made the first fine measurement between the forces between charges. Coulomb = C and has a charge of 6 X 10 18 Protons or electrons
6. The unit of C can apply to both positive and negative charge
7. Electric forces Like charges repeal each other and unlike charges attract each other Works with electroscope
8. Electric current Formula is: I = q/t I = current in amps . Q = charge that flows . t = Time for charge to flow in seconds
9. Electric current Say that current is the movement of electric charge through a circuit. Eg. A current of 10 amperes means that 10 amperes of charge flow through the wire every second. Drift velocity is caused by an applied voltage added to random bouncing thus causing electrical current.
10. Conductors and insulators electrons in a conductor with current move opposite the current flow Electrons in an insulator do not move at all Electrons in a semiconductor has a few free electrons to move with the current flows.
11. Static electricity and Polarization Charging by friction causes the attraction of objects Polarization of objects causes the insulated material to have electrons go to one side. Conductors the entire object becomes polarized.
12. Coulomb’s law F = K q1 q2/ r2 F = force in Newton's K = a constant 9 X 109 N m2 / C2 . q = charges . r = Distance (m)
13. Coulomb’s Law The force between charges is directly proportional to the magnitude or amount of each charge. The force between charges is inversely proportional to the square of the distance between them. Or the inverse square law goes into effect.
14. Coulomb’ s law Used to calculate point charges Electric forces always occurs in pairs according to Newton’s third law of motion
15. Electric fields Gravitational field strength = F = mg Electric field strength = F= qE F = Force . q = charge E = electric field Strength of the field = N/kg
16. Information One volt is one joule/coulomb A joule is equal to a newton-meter Newton/C = one volt per meter
17. Capacitors Is a storage device for electric charges Can be charged by connecting it battery Can be discharged by connecting It to any closed circuit that allows current to flow
18. Capacitors The current flowing into or out a particular capacitor depends on four things: 1. The amount of charge already in the capacitor. 2. The voltage applied to the capacitor by the circuit. 3. Any circuit resistance that limits the current flowing in the circuit
19. Capacitors 4. The capacitance of the capacitor. The amount of charge in a capacitor depends on the following: 1. The voltage applied to the capacitor 2. The insulating ability of the material between the positive and negative plates
20. Capacitors 3. The area of the two plates ( larger > smaller) 4. The separation distance between the plates
21. Capacitance . q = CV . q = Charge (C) C = Capacitance C?V V = voltage (V)