PHYS 102 1st EditionExam # 1 Study Guide Lectures: 1 - 14Lecture 1 (August 18)Properties of Electric Charges What are some common properties that electric charges have? Some common properties electric charges have are: 1. Unlike charges attract one another and like charges repel one another. 2. Electric charge is always conserved. 3. Charge comes in discrete packets that are integral multiples of the basic electric charge e = 1.6 X 10-19 . 4. The force between two charged particles is proportional to the inverse square of the distance between them. Applications of electric charges: Finding the net charge of an atom. 1. For example, there is an atom with 3 protons, 3 electrons, and 3 neutrons. What is the total (net) charge of the atom? Q = 3 (q)proton + 3(q)electron + 3(q)neutron(q)proton = +1.6 X 10-19  (q)electron = -1.6 X 10-19  (q)neutron = no charge= 3 (+1.6 X 10-19) + 3(-1.6 X 10-19) = 0  thus, the atom is uncharged. Lecture 2 (August 20) What does Coulomb’s Law state? How can we use it to find the force between two stationary charged particles? Coulomb’s law states that the electric force between two stationary charged particles separated by a distance r has the magnitude: F = k[(q1 X q2)/r2] , where q1 and q2 are the magnitudes of the charges on the particles in coulombs and k= 8.99 X 109 Nm2/C2 is the Coulomb constant. Distance is important for this force; when two objects are attracted to each other there is a force. The force of attraction between the 2 is dependent on q1, and the bigger q1, the bigger the F.Lecture 3 (August 22)What is an electric field? What can we use electric field lines for? An electric field is an electric disturbance in a region surrounding a charge. If you place a second charge in this region, the second charge will feel the electric force of the first charge. Fon q2 = q2Eby q1  F = qEThe number of electric field lines or E-lines is proportional to the strength (magnitude) of Q. Electric field lines run outward from +q and inward to –q. Electric field lines can be thought of assimilar to forces, in that two positive E-lines will collide, but instead they turn to avoid each other (like similarly charged objects repel each other). Lecture 4 (August 25) How do you utilize Coulomb’s Law in order to find the net force of q1 on q2 or q2 on q3? How do you determine the direction of the net force between two charges? q1= +6 C , q2= +1.5 C, q3= -2 C, r from q1 to q2= 3 cm, r from q2 to q3= 2 cm = 10-6 & cm = 1/100 m & k= 9 X 109Net force on q1: F1 = k[(q1q2)/r2] = (9 X 109)[(6 X 10-6)(1.5 X 10-6)/(3/100)2] = 89.9 N Net force on q2: F2 = k[(q1q3)/r2] = (9 X 109)[(6 X 10-6)(-2 X 10-6)/(5/100)2] = 43.2 N Net force on q3: F3 = k[(q2q3)/r2] = (9 X 109)[(1.5 X 10-6)(-2 X 10-6)/(2/100)2] = 67.4 N The direction the force goes in depends on the charges of the two forces. Lecture 5 (August 27) What is electric potential difference? The electric potential difference V between points A and B is the change in electric potential energy as a charge q moves from A to B divided by the charge q: V = VB-VA = PE/q. SIunit is J/C or Volts. Lecture 6 (August 29) How do you relate work to the electric potential difference? What is EKG? How do you calculate the electric potential difference for certain points? V = PE/q AND Work =KE or = -PE  so, Work = V/q EKG is measuring voltage of the heart on the skin. Voltage and electric fields are related. V = -Ed ; where E is the electric field and d is distance. In order to calculate the electric potential difference for two points, you can use the following equations: Va = kq-/r and Vb= kq+/rLecture 7 (September 3)What is capacitance? What is a capacitor? Capacitance (C) is the value or magnitude of a device called capacitor. Capacitors store electric energy like water tanks store water. Capacitors come in many shapes/types. The most common type is the parallel-plate capacitor. Capacitance can be calculated using: C = Q/V; where Q is for one plate and V is the voltage across the plates. You can also use: C = (A/D); where  is the medium between the plates, A is the area of one plate, and D is the distance between the plates. For air, = 8.85 X 10-12. Lecture 8 (September 5) How do you calculate the capacitance between a cloud and Earth? How do you calculate the electric potential difference between the two? To calculate the capacitance, you would use C = (A/D); where  is 8.85 X 10-12, the A is the area of the cloud (or Earth), and d is the distance between the two. The units would be Farads, which is C/J. To calculate the electric potential difference you would use V = -Ed; whereE is the electric field value and d is the distance between the two. The units would be volts. Once you have both values, you could solve for Q using, Q = CV. The units for Q would Coulombs. Lecture 9 (September 8)What is the average electric current in a conductor defined as? What is the equation used to solve for the electric current? Current is the time rate of flow of charge through a surface. You can solve for the average electric current by using this equation: I = Q/t; where Q is the charge that passes through a cross section of the conductor in time t. Lecture 10 (September 10)What is Ohm’s Law? What is resistance? How do you solve for resistance? Ohm’s Law describes many conductors for which the applied voltage is directly proportional to the current it causes. The proportionality constant is the resistance: V = IR. The resistance R ofa conductor is defines as the ratio of the potential difference across the conductor to the current in it: R = V/I. If a conductor has a length l and cross-sectional area A, its resistance is R=R0 (l/A); where R0 is the resistivity of the material, which is material dependent. Lecture 11 (September 12) What is power defined as? How do you solve for power? Power can be defined as the rate at which energy is supplied to the device. You can solve for power using P = IV, if the potential difference V is maintained across an electrical device. Lecture 12 (September 15) How do you solve for the required resistance of a system? How do you solve for the length ofwire required to wind a coil? What light bulb would have a higher R and a higher I? You would solve for the required resistance of a system by using I = V/R and solving for R. You would solve for the length of wire required to wind a coil by