On pages 120, 121, and 121b we learn how to detect magnetic fields with a compass and to measure them with a tangent galvanometer.

The Chapter Review Sheet should be started now.

On pages 122 and 123 we discover the magnetic field generated by a current-carrying wire, we map the curved field lines produced when such a wire is in a pre-existing uniform field, and we use that map to predict and then measure the magnetic force on such a wire.

On pages 124 & 124b we complete the new magnetic force law by inventing a standard unit for field strength, and then solve some practice exercises.

On pages 125 and 126 we discover that a magnetic field can exert force on a moving charged particle. Then we figure out how to predict the path radius of such a particle moving through a uniform field.

On pages 127 & 128 we measure the mass of an electron by using magnetic deflection, and then tackle several related problems.