SECTION 1: SHADE IN THE LETTER OF THE BEST ANSWER ON THE BUBBLE SHEET. (60%)

Transcription

1 PHYSICS 3204 Unit 2 Test #1 NAME: SECTION 1: SHADE IN THE LETTER OF THE BEST ANSWER ON THE BUBBLE SHEET. (60%) 1 The elementary charge is the amount of charge on -?-. A) an atom B) a proton C) an electron D) both B) and C) 2 A negative charge will reside on the outside surface of a conductor because of the -?- A) attraction of electrons to protons B) attraction of protons to electrons C) repulsion of protons D) repulsion of electrons 3 What is the significant property of an insulator? A) insulators permit easy movement of electrons through them B) insulators do not permit easy movement of electrons through them C) insulators must be charged by conductors D) insulators must be supported by a conductor before being charged 4 Part of the fundamental law of electric charges states that -?- A) like charges attract each other B) opposite charges repel each other C) charged objects and neutral objects can attract each other D) charged objects and neutral objects can repel each other 5 While a positively charged rod moves closer and closer to a charged electroscope the leaves collapse and then repel each other again. The charge on the electroscope is -?- A) positive B) negative C) could be either A) or B) D) impossible to tell for sure 6 Two identical metal spheres are given charges of +6.0 C and -4.0 C. If the two spheres are touched together and then separated, what will be the charge on each sphere? A) -10 C B) 0 C C) +1.0 C D) +2.0 C 7 19 A lightning strike transfers 1.25 x 10 electrons to the ground. How much charge is this? -38 A) 1.3 x 10 C -19 B) 1.6 x 10 C C) 2.0 C 37 D) 7.8 x 10 C 8 Two charged objects experience a repulsive force of 0.08 N. What will the new force be if both charges are doubled? A) 0.04 N B) 0.08 N C) 0.16 N D) 0.32 N

2 9 According to Coulomb s Law, the electric force between two charged objects is -?- A) directly proportional to the product of the charges. B) directly proportional to the square of the charges. C) inversely proportional to the distance between them. D) directly proportional to the distance between them. 10 In the case shown all three objects have an equal amount of charge. Objects A and C are positive, and B is negative. The net force on B is in the direction -?- A) towards A B) straight upward from B C) towards C D) straight down from B 11 Three equal charges are arranged as shown. Objects P and Q are positively charged, while object R is negatively charged. Which arrow best describes the direction of the net electrical force on object Q? A) A B) B C) C D) D

3 12 Which of the following statements about an electric field is FALSE? A) the lines of force meet the charged object at right angles B) the lines of force never touch or cross each other C) the field is 3-dimensional D) the lines of force point in the direction in which a small negative test charge would move 13 6 What electric force is exerted on a small test charge of 2.4 x 10 C when it is placed in an 4 electric field of strength 3.5 x 10 N/C? 11 A) 6.9 x 10 N -2 B) 8.4 x 10 N C) 1.2 N 10 D) 1.5 x 10 N 14 What is the electric field strength at a point 10 cm from a Van de Graaf generator that has a charge of 4.5 C on it? 2 A) 4.05 x 10 N/C 6 B) 4.05 x 10 N/C 8 C) 4.05 x 10 N/C 9 D) 4.05 x 10 N/C 15 A Van de Graaf generator has a charge of 1.0 mc on it. When a test charge of +1.0 C is placed 0.50 m from the generator, the force exerted on it is 36 N. What is the electric field strength at this point? A) 0 N/C B) 36 N/C 4 7 C) 3.6 x 10 N/C D) 3.6 x 10 N/C 16 What is the magnitude of the electric field strength at point P, midway between the two fixed charges shown below? A) 0 5 B) 4.0 x 10 N/C 5 C) 1.0 x 10 N/C 5 D) 8.0 x 10 N/C 17 Which diagram correctly illustrates the electric field near a negative point charge? 18 The safest place to be during a lightning storm is -?- A) at the centre of a large metal drum B) in a rowboat on a lake C) standing on a rubber mat D) under a large tree

4 19 A 12 V car battery moves 400 C of charge through the wires while starting the car. How much energy is used by the battery during this event? A) 0.03 J B) 12 J C) 33.3 J D) 4800 J 20 3 A charge of 1.5 C is moved 5.0 cm through an electric field of strength 2.5 x 10 N/C. How much electric potential energy did the charge gain? 4 A) 1.9 x 10 J 2 B) 1.9 x 10 J C) 1.90 J D) 190 J

5 SECTION 2: ANSWER ALL OF THE FOLLOWING PROBLEMS ON THIS PAPER. (40%) 21 For the case shown below, determine the net force on object B. (20%) Q A = +1.0 C A B Q B = +2.0 C Q C = +4.0 C d AB = 20 cm d = 35 cm BC C

6 22 With the aid of diagrams, explain how a neutral electroscope can be given a permanent charge by induction, using a negatively charged rod. (10%) 23 Carefully sketch the electric field lines in the region surrounding the three objects. (10%) BONUS QUESTION (Maximum 5 %) Wire fences are often known to become negatively charged during periods of blowing snow, and sparks are sometimes seen to fly off the tips of the wire. Use the principles of electrostatics to explain these two events.