Evans SPH 3U1

Physics Grade 11

Unit 5: Electricity & Magnetism

Note 11: The Motor


Reference: Chapter 17.4


The Motor Principle:

Two magnetic fields interact with each other to produce a force. If a conductor carrying a current passes through a magnetic field, it experiences a force perpendicular to the conductor's charge flow and the external magnetic field.


Right Hand Rule #3 for the Motor Principle (for conventional current flow - NOT electron flow):

If the fingers of the open right hand point in the direction of the external magnetic field (from North to South), and the thumb point in the direction of the current, the force on the conductor will be in the direction in which the right palm faces.


Using RHR #3 Fig. 17.19, 17.20 (remember thumb positive current, fingers magnetic field N to S, palm force)


Operation of a motor

LAB: Build a motor


Complete student worksheets 13.5, 13.6 (3 sheets) from Nelson.