Physics 100B - Answer Key

Practice Quiz 1 Physics 100B 1) When the distance between the two charges is doubled, the force between them is A) doubled. B) quadrupled. C) reduced by a factor of 3. D) reduced by a factor of 4. Answer: D 2) When the magnitude of two charges is increased by a factor of 2, the electrical forces between these charges is A) doubled. B) quadrupled. C) reduced by a factor of 3. D) reduced by a factor of 4. Answer: B 3) Two charges, Q1 and Q 2, are separated by a certain distance R. If the magnitude of their charges is halved, and their separation is doubled, then what happens to the electrical forces between these charges? A) It decreases by a factor of 4. B) It decreases by a factor of 8. C) It decreases by a factor of 16. D) It remains t he same. Answer: C 4) Four equal charges are located at the corners of a square of side d. If the magnitude of each charge is doubled and the length of each side of the square is also doubled then what happens to the resultant force on each charge? A) It is doubled. B) It is quadrupled. C) It remains the same. D) It decreases by a factor of 4. Answer: C 5) The magnitude of a force between two equal charges is 4 N when the separation is 2 m. If the charge separation becomes 6 m, then what happens to the magnitude of the force between them? A) It remains the same. B) It decreases by a factor of 4. C) It is 4/9 N. D) None of the other choices is correct. Answer: C Figure 1. 6) Four point charges of equal magnitude and signs are arranged on three of the corners and at the center of the square of side d as shown in Figure 1. Which of the arrows shown represents the net force acting on the center charge? A) A B) B C) C D) D Answer: B Figure 2 7) Four point charges of equal magnitude and varying signs are arranged on corners of the square of side d as shown in Figure 2. Which of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square? A) A B) B C) C D) D Answer: B 8) The charge on the proton is the same as A) the charge on the neutron. B) the charge on the atom. C) the charge on the electron. D) the charge on the electron, but of the opposite sign. Answer: D 9) Two charges, Q1 and Q 2, are separated by a certain distance. The ratio of charge Q 1 to charge Q2 is 1:2. The ratio of force on Q1 to the force on Q 2 is A) 1:2. B) 1:1. C) 2:1. D) None of the other choices is correct. Answer: B 10) Two charges, Q 1 and Q2, are separated by a certain distance R. If the magnitudes of their charges are doubled and their separation is halved, then what happens to the electrical force between these charges? A) It increases by a factor of 16. B) It stays the same. C) It is doubled. D) It is quadrupled. Answer: A 11) Two point charges of +30.0 µC and -9.00 µC are separated by a distance of 20.0 cm. What is the intensity of electric field E midway between these two charges? A) 35.1 × 106 N/C directed towards the negative charge B) 35.1 × 106 N/C directed towards the positive charge C) 35.1 × 105 N/C directed towards the negative charge D) 35.1 × 105 N/C directed towards the positive charge Answer: A