6.2 ELECTRIC FORCE AND FIELD HW Study Packet

Transcription

1 6.2 ELECTRIC FORCE AND FIELD HW Study Packet Required: READ Hamper Tsokos, pp SL / HL Supplemental: Cutnell and Johnson, pp DO Tsokos p 287 #3,7,9 pp #4,6,11,12 REMEMBER TO. Work through all of the example problems in the texts as you are reading them Refer to the IB Physics Guide for details on what you need to know about this topic Refer to the Study Guides for suggested exercises to do each day First try to do these problems using only what is provided to you from the IB Data Booklet Refer to the solutions/key ONLY after you have attempted the problems to the best of your ability UNIT OUTLINE I. ELECTRIC CHARGE A. TYPES OF CHARGE B. CONSERVATION OF CHARGE II. COULOMB S LAW A. FORCES BETWEEN CHARGES B. FORCES IN MULTIPLE CHARGE CONFIGURATIONS III. ELECTRIC FIELD STRENGTH A. FORCE FIELDS B. THE ELECTRIC FIELD DUE TO ONE POINT CHARGE C. THE ELECTRIC FIELD DUE TO TWO OR MORE POINT CHARGES FROM THE IB DATA BOOKLET WHAT YOU SHOULD BE ABLE TO DO AT THE END OF THIS TOPIC Describe and differentiate between the methods of charging by friction and electrostatic induction Understand the use of the electroscope Recognize that charge resides on the outside surface of a conductor and that the net charge (and electric field) inside a conductor is zero Use Coulomb s Law in problem-solving Determine electric field strength due to one or more point charges Recognize that a charge placed in an electric field experience a force Understand that the electric field of a point or spherical charge is radial Understand that the electric field between 2 parallel plates is uniform with an edge effect Draw the electric field patterns for different charge configurations State the similarities and differences between gravity and electricity Solve problems involving electric charges, forces, and fields 1

2 HOMEWORK PROBLEMS: 1. Lightning occurs when there is a flow of electric charge (principally electrons) between the ground and a thundercloud. The maximum rate of charge flow in a lightning bolt is about 20,000.0 C/s; this lasts for s. How much charge flows between the ground and the cloud in this time? How many electrons flow during this time? [2 C, 1.25 x ] * 2. Excess electrons are placed on a small lead sphere of mass 10.0 g so that the net charge is 2.40 x C. a) Find the number of excess electrons on the sphere. [1.5 x 10 9 ] * b) How many excess electrons are there per lead atom? The atomic number of lead is 82, and its atomic mass is 207 g/mol. [5.2 x ] * 3. Find the forces F AB and F BA in each of these two cases: a) b) [F AB = -6.7 x 10 9 N, F BA = +6.7 x 10 9 N] [F AB = +6.7 x 10 9 N, F BA = -6.7 x 10 9 N] 2

3 4. Two charges q 1 and q 2 are arranged as shown. If q 3 = 4.0 x 10-6 C and the distance between q 1 and q 2 is 5.0 m, calculate the distance between q 1 and q 3 so that the force on q 3 is zero. [2.2 m] 5. Calculate the total force on q 3 below. 3

4 6. Four point charges of equal magnitude are held at the corners of a square as shown. The length of each side of the square is and the sign of the charges is as shown. The point P is at the centre of the square. +Q +Q a) Deduce that the magnitude of the electric field strength at kq point P due to one of the point charges is equal to. 2 P Q Q b) On the diagram, draw an arrow to represent the direction of the resultant electric field at point P. c) Determine, in terms of Q, a and k, the magnitude of the electric field strength at point P. 7. What is the magnitude of an electric field in which the electrical force of a proton is equal in magnitude to its weight? [1.02 x 10-7 NC -1 ] 8. Two particles having charges q 1 = 1.00 nc and q 2 = 3.00 nc are separated by a distance of 1.20 m. At what point along the line connecting the two charges is the total electric field due to the two charges equal to zero? [43.9 cm from q 1 ] 4

5 9. A small object carrying a charge of 4.00 nc experiences a downward force of 5.00 x 10 8 N when placed at a certain point in an electric field. a) What are the magnitude and direction of the electric field at this point? [12.5 NC -1 up] b) What would be the magnitude and direction of the force acting on a proton placed at the same point in the electric field? [2.0 x N up] 10. Two parallel, charged metal plates A and B are in a vacuum. At a particular instant an electron is at point P. On the diagram, draw: a) the electric field pattern due to the plates. b) an arrow to represent the direction of the force on the electron at P. c) The acceleration of the electron at P is m s -2. Determine the magnitude of the electric field strength at the point P. [ N C -1 /V m -1 ] * d) The electric potential energy of the electron changes by J as it moves from one plate to the other. Show that the potential difference between the plates is 120 V. 5