Suppose you set up the apparatus as described in the manual to determine the zero reference current I0. Then with the anode voltage set to V = 22.5 V, you adjust the Helmholtz coil current I = Ii so that the outer edge of the electron beam hits the outermost post. Without changing anything else you now change the anode voltage to V = 45 V (exactly twice what it was before). What new value of I = If do you need so that the outer edge of the electron beam again hits the outermost post? If = 2 (Ii I0 ) I0 If = 1 2 (Ii I0 ) I0 If = 2 Ii If = 1 2 Ii If = 2 (Ii I0 ) I0 If = 1 2 Ii If = 1 2 (Ii I0 ) I0 If = 4 (Ii I0 ) I0 If = 4 Ii If = 2