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An Introduction to the Physics of simple DC Electric Motors
Rating: 4.4 out of 5(70 ratings)
2,617 students
Created byJohn Moylan
Last updated 5/2020
English

What you'll learn

  • This is a senior high school level physics course.
  • Please check out the preview lectures, and the detailed course description, before enrolling.
  • Calculating the force on a moving electrric charge in a magnetic field
  • Calculating the force on a current carrying wire due to a magnetic field
  • Calculating the force between parallel current carrying wires
  • Introduction to torque, and how to calculate torque
  • The physics of the forces on a current carrying loop in a magnetic field
  • Calculating the torque on a current carrying loop in a magnetic field
  • Introduction to simple DC electric motors
  • Building a simple DC electric motor

Course content

3 sections • 13 lectures • 1h 9m total length

  • Introduction3:20

    Welcome to the course.

    Electric motors are increasingly important to the modern world, and direct current motors especially so.  There are many DC electric motors in modern cars, consumer items, computers, and other electrical items.  This course outlines, starting from basic physical principles, how and why DC electric motors work, practically, conceptually and in terms of mathematical descriptions.  The basic components of a DC electric motor are also outlined, in terms of what these components do and how they work.  During the course you will have the opportunity to build simple working electric motors in order to help your understanding.

    The course starts from a the most basic of physical principles underlying all electric motors, the force generated on a moving charge by a magnetic field, then goes on to consider the force on a current carrying conductor due to a magnetic field, which is  known as the motor effect, and how to calculate this force.  The force between parallel charge carrying conductors is also discussed and treated mathematically.

    You will get to make a working homo-polar electric motor, and understand the physics of how it works.

    Most electric motors are based on the forces operating on a current carrying loop in a magnetic field, and these are explained, together with how to calculate the torque on a current carrying coil in a magnetic field, as well as the nature of torque itself and how to calculate it

    You will learn the about the role of the commutator in direct current electric motors, and the physics of why commutators necessary.  You will also learn about different types of magnetic fields in electric motors and the effect that these can have on the operations of electric motors.

    You will also get to make a working direct current electric motor with a commutator.

    There is a list of the equipment you will need for the projects in this course in the description.  These projects have been designed to be inexpensive to complete, and the equipment is only suggested, use your imagination to substitute other things, such as Styrofoam for cardboard, and so on.

    As well as these things you will learn how devices such as galvanometers and loud speakers work.

    For HSC students there are many past exam questions with worked solutions, and complete coverage of topic 9.3.1, the Motor Effect.  As well as this, you get to make two working electric motors!

    For people enrolling in the course out of interest, you will get to understand the physics of DC electric motors, and make two working electric motors. 

    Please use the Q&A tab to ask questions and participate in discussions.  I will always try to answer questions within 24 hours, and will usually answer questions well under half this time. 

    I hope that you find the course both enjoyable and informative.


    Possible equipment needed to build projects:

    Two neodymium magnets.

    Enameled copper wire.

    Hook up wire.

    A battery (AA or similar).

    A wood screw.

    Two or three rubber bands.

    Cardboard or timber off cuts.

    A drinking straw.

    A wooden skewer.

    Glue or a glue gun.

    A hobby knife and/or scissors.

    Sandpaper.

    Sticky tape.


  • Charged Particles in Magnetic Fields4:01

    The nature of the magnetic field surrounding a moving charged particle, and the force on a moving charged particle due to a magnetic field.

    This is background material for HSC Physics Syllabus dot point 9.3.1, and also covers dot point 9.4.1.2.3 from the next topic in the syllabus.

  • Force on a Current Carrying Conductor in a Magnetic Field8:31

    The physics underlying the force on a charge carrying conductor in a magnetic field, and how to calculate this force.

    Notes for this lecture include the worked examples covered in the next lecture.

  • Calculating the Force on a Current Carrying Conductor - Worked Examples10:53

    Worked solutions for past HSC exam questions.

    Questions and written solutions are in the notes for the last lecture.

    Questions:

    1, based on 2010 HSC question 28

    2, based on 2012 HSC question 8

    3, based on 2013 HSC question 3

  • Practical Exercise, Building a Homopolar Electric MotorMotor1:14

    Build a simple electric motor.

  • The Force Between Parallel Current Carrying Conductors7:34

    The physics underlying the force operating between parallel current carrying conductors, and how to calculate this force.

  • Force on a Current Carrying Conductor in a Magnetic Field

Requirements

  • This course is at high performing senior high school students
  • High level mathematical ability
  • Have a high level understanding of electricity, magnetism and forces.

Description

This is a Physics course, not an engineering course, or a mechanics course. 

The course covers the Physics of the motor effect, the force on a moving electric charge due to a magnetic field, and builds on this to cover the force on moving conductors, and finally the physics of simple DC electric motors.

Please check out the preview lectures and lecture descriptions.  

The course aims to gradually build your understanding of the physics underlying electric motors.  As such it begins by examining the interaction between moving charged particles and magnetic fields, and how a moving electric charge in a magnetic field generates a force, which when the charge is moving through a conductor causes a force on the conductor.  Calculating the forces on an isolated moving charge and an electric charge moving through a conductor are both outlined, with worked examples in the notes.  Building on this the course goes on to consider the forces on a current carrying loop in a magnetic field, the calculation of torque, the calculation of the torque on a current carrying loop in a magnetic field.  The final section of the course explains the operation of simple DC electric motors in terms of the physical concepts introduced earlier in the course.  You will have the opportunity to build a simple DC electric motor.

This course will teach you about the physics of the motion of electric charges in magnetic fields that results in the motor effect, and how this is exploited in simple DC electric motors.







Who this course is for:

  • Students studying Physics for the New South Wales Higher School Certificate.
  • Anyone teaching high school physics.
  • Anyone who wishes to understand the interaction between electric and magnetic fields underlying the motor effect.

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