Phys102 Term: 131 Online HW-Ch28-Lec02 Q1: A uniform magnetic field is directed into the page. A Charged particle, moving in the plane of the page, follows a clockwise spiral of decreasing radius as shown. A reasonable explanation is: A. B. C. D. E. the charge is positive and slowing down the charge is negative and slowing down the charge is positive and speeding up the charge is negative and speeding up none of the above Ans: B Q2: An proton with a velocity of v = − 3.0 × 105 ı̂ (m/s) enters a region of space where there is a magnetic field given by B = − 5.0 × 10 − 4 ȷ̂ (T). What is the frequency of revolution of the proton? (Give the answer in three significant figures and SI units) Ans: = f qB 5 ×10−4 ×1.6 ×10−19 = = 13.98 ×106 Hz −31 2π m 6.28 × 9.11×10 f = 14.0 MHz Q3: A long straight wire carries a 6.0-A current that is directed in the positive x direction. When a uniform magnetic field is applied perpendicular to a 3.0-m segment of the wire, the magnetic force on the segment is 0.36 N, directed in the negative y direction. What is the magnetic field? (Give the answer in three significant figures and SI units) Ans: F= iL × B F = iL × B × sin (θ) = B Fmax 0.36 = = 20.0 mT i× L 6×3 KFUPM-Physics Department 1