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Unformatted text preview: gilvin (jg47854) – 16. Magnetic fields 1 – meyers – (21235) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A proton traveling to the right along the x- axis enters a region where there is a mag- netic field of magnitude 1.1 T directed upward along the y-axis. The charge on a proton is 1.60 × 10- 19 . If the proton experiences a force of 2 . 7 × 10- 12 N, find its speed. Correct answer: 1 . 53409 × 10 7 m / s. Explanation: Let : B = 1 . 1 T , F m = 2 . 7 × 10- 12 N , and q e = 1 . 60 × 10- 19 C . The magnetic force is F m = q v B v = F m q B = 2 . 7 × 10- 12 N (1 . 6 × 10- 19 C) (1 . 1 T) = 1 . 53409 × 10 7 m / s 002 10.0 points An electron is in a uniform magnetic field B that is directed out of the plane of the page, as shown. v e- B B B B When the electron is moving in the plane of the page in the direction indicated by the arrow, the force on the electron is directed 1. toward the left 2. into the page. 3. out of the page. 4. toward the top of the page. 5. toward the right 6. toward the bottom of the page. correct Explanation: The force on the electron is vector F = q vectorv × vector B = − e vectorv × vector B. The direction of the force is thus hatwide F = − hatwide v × hatwide B , pointing toward the bottom of the page , us- ing right hand rule for hatwide v × hatwide B , and reversing the direction due to the negative charge on the electron. 003 10.0 points The magnetic field at the equator points north. If you throw a positively charged object (for example, a baseball with some electrons removed) to the east, what is the direction of the magnetic force on the object? 1. Toward the west 2. Upward correct 3. Toward the east 4. Downward Explanation: Use the right-hand rule: point your index finger east and your middle finger north. Your thumb points upward (representing the force on a positively charged object). 004 (part 1 of 2) 10.0 points gilvin (jg47854) – 16. Magnetic fields 1 – meyers – (21235) 2 In a nuclear research laboratory, a proton moves in a particle accelerator through a mag- netic field of intensity 0 . 227 T at a speed of 3 . 67 × 10 7 m / s....
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This note was uploaded on 04/29/2011 for the course PHYS 202 taught by Professor Doc during the Spring '11 term at North Texas.
- Spring '11