Chapter 21 Electric Charge and electric Field Charles

21 -4 Induced Charge; the Electroscope Metal objects can be charged by conduction: Charles

21 -4 Induced Charge; the Electroscope They can also be charged by induction, either

21 -4 Induced Charge; the Electroscope Nonconductors won’t become charged by conduction or induction,

21 -4 Induced Charge; the Electroscope The electroscope can be used for detecting charge.

21 -4 Induced Charge; the Electroscope The electroscope can be charged either by induction

Electroscope https: //www. youtube. com/watch? v=-Js. VZwc 1 d. Oo Charles Allison © 2000

21 -5 Coulomb’s Law Experiment shows that the electric force between two charges is

Coulomb’s Law The magnitude of the electric force two charges exert on each other

21 -5 Coulomb’s Law The force is along the line connecting the charges, and

21 -5 Coulomb’s Law Unit of charge: coulomb, C. The proportionality constant in Coulomb’s

21 -5 Coulomb’s Law Q 1 Q 2 + a) c) - + F

Question An particle with a charge +2 e and a mass of 4 mp

Problem 11 11. (II) Two positive point charges are a fixed distance apart. The

Problem 12 12. (II) Particles of charge +75 μC, +48μC, and -85μC are placed

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21 -5 Coulomb’s Law Experiment shows that the electric force between two charges is proportional to the product of the charges and inversely proportional to the distance between them. Charles Allison © 2000

Coulomb’s Law The magnitude of the electric force two charges exert on each other q 1 q 2 • This is the magnitude of the force k = 8. 99 x 10+9 Nm 2/C 2 = coulomb’s constant • Direction: – always along a line between the two charges – Can be attractive or repulsive depending on the signs of the charges – Forces on the two charges are equal in magnitude and opposite in direction Charles Allison © 2000

21 -5 Coulomb’s Law Unit of charge: coulomb, C. The proportionality constant in Coulomb’s law is then: k = 8. 99 x 109 N·m 2/C 2. Charges produced by rubbing are typically around a microcoulomb: 1 μC = 10 -6 C. Charles Allison © 2000

21 -5 Coulomb’s Law Q 1 Q 2 + a) c) - + F 31 3 F 32 Q 3 Question What is the correct Forces Diagram for charge 3 where F 31 is the force on Q 3 due to Q 1 and F 32 is the force on Q 3 due to Q 2? b) d) 3 F 32 F 31 3 F 32 Charles Allison © 2000

A) F = Fp B) 2 F = Fp C) 4 F = Fp D) F = 2 Fp E) F = 4 Fp Charge +2 e p +e Mass 4 mp mp Question An particle with a charge +2 e and a mass of 4 mp is on a collision course with a proton with a charge +e and mass mp. The only force acting is the electrostatic force. Which of the following statements is true about the magnitudes of the forces on the two particles? Charles Allison © 2000

Question An particle with a charge +2 e and a mass of 4 mp is on a collision course with a proton with a charge +e and mass mp. The only force acting is the electrostatic force. Which of the following statements is true about the accelerations of the two particles? A) a = ap B) 2 a = ap C) 4 a = ap D) a = 2 ap E) a = 4 ap Charge +2 e p +e Mass 4 mp mp Charles Allison © 2000

Problem 11 11. (II) Two positive point charges are a fixed distance apart. The sum of their charges is QT. What charge must each have in order to (a) maximize the electric force between them, and (b) minimize it? Charles Allison © 2000

Problem 12 12. (II) Particles of charge +75 μC, +48μC, and -85μC are placed in a line (Fig. 21– 52). The center one is 0. 35 m from each of the others. Calculate the net force on each charge due to the other two. Charles Allison © 2000