1. In his famous experiment with electrons , J. J. Thomson measured the "charge to mass ratio " (y = e/m ), where e is the electron's charge and m is its mass. A modern classroom version of this experiment finds the ratio y by accelerating electrons through a voltage and then bending them in a magnetic field . the ratio (y = e/m ) is given by, 125 D2V 32 /1 2 NV 2 d212 In this equation #, is the permeability constant of the vacuum (equal to 4x x 10-7 N/m?) and N is the number of turns in the coil that produces the magnetic f field , D is the diameter of the coil , V is the voltage that accelerates the electrons , d is the diameter of the electron's curved path and / is the current in the field coil. A student makes the following measurements, N = 72 D = (661 + 2) mm V = (45 .0 + 0.2) V d = (91 .4 + 0.5) mm 1 = (2.48 + 0.04) A (a) Find the student's answer for the charge-to-mass ratio of the electron and find uncertainty in it. Quote your results (mean value uncertainty ) units. (b) How well does the answer agree with the accepted value (y = 1.759 x 10 " C/kg)? 2. When a torsion wire of radius r and length ' is fixed at one end and subjected to a moment c at the other , the angular displacement p is given by, 2'c P = where n is the rigidity modulus of the material of the wire. The following values are obtained (4.00 + 0.12 ) rad N -1 m-1, y = 1.00 + 0.02 mm , = 500 # 1 mm