(3) Suppose that when the Helmholtz coils are viewed from the front the conventional current goes around the coils counter-clockwise, what direction does that imply for the roughly uniform magnetic field in the coils? The magnetic field in the Helmholtz coils is given by

B=(45)32?0Inr

(4) Given a current of1.60 A, a number of windings in each coil ofn = 130, and that the radius of the coils is15.0 cm, find the magnitude of the magnetic field in the Helmholtz coils.

(5) electrons moving counter-clockwise in a circle, does this imply that the current in the Helmholtz coils is clockwise or counter-clockwise? Hint: find the direction of the magnetic field influencing the electrons first. e/m Based on the amount of magnetic field in the coils, the voltage on the electron gun, and the measured radius of the electron beam an experimental value of the ratio of the electron charge to the electron mass can be found. It can be shown that the correct formula is e 2AV R2 B2