Motors. Book pg Syllabus /09/2016. The Butterfly Effect. cgrahamphysics.com 2015

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1 Motors Book pg Syllabus /09/2016 The Butterfly Effect

2 The Motor effect where?

3 What device does not use a motor?

4 Aim Know the link between movement, magnetism and current Know how electric motors work Use Fleming s left hand rule or the 3rd right hand rule Key words Motor effect Electromagnetism Fleming s rule or RHR #3 - motor - commutator - brushes

5 Have you ever wondered How would a world without motors look like? The bigger picture

6 What is a motor? An electric motor is a device that converts electrical energy into mechanical energy to produce a turning effect. Most motors are powered using direct current (DC), which is produced by cells and batteries. Which devices in your home use an electric motor?

7 The Motor Effect If a wire carrying a current is placed into a magnetic field, an interesting thing happens. As part of the GCSE course, you are required to know which way a wire placed into a magnetic field moves

8 Fleming s left hand rule F = force on wire B = external magnetic field I = current

9 Right Hand rule # 3

The motor effect 10 of 26 Boardworks Ltd 2012 When current flows through a wire held in a magnetic field, it can create a force that moves the wire. force This is called the motor effect.

10 The motor effect 10 of 26 Boardworks Ltd 2012 When current flows through a wire held in a magnetic field, it can create a force that moves the wire. force This is called the motor effect. If the magnetic field and current are at right angles to each other, this results in the maximum force possible on the wire. If the magnetic field and current are parallel to each other, there is no force. What do you think happens if the wire is held at a different angle to the magnetic field?

11 Wire in a magnetic field 11 of 26 Boardworks Ltd 2012

reversing the current reversing the magnetic field The direction of the force

12 Changing the direction of the force 12 of 26 Boardworks Ltd 2012 The direction of the force acting on a wire in an electromagnetic field can be reversed by: reversing the current reversing the magnetic field The direction of the force is therefore relative to both the direction of the magnetic field and the current.

13 Increasing the size of the force 13 of 26 Boardworks Ltd 2012

14 The motor effect: true or false? 14 of 26 Boardworks Ltd 2012

15 How can we turn a wire into a motor? One wire won t make a motor How about a complete loop?

16 Coil in a magnetic field 16 of 26 Boardworks Ltd 2012

17 DC electric motor simulation 17 of 26 Boardworks Ltd 2012

This happens when the current-carrying coil and the lines of force from the permanent magnets are

18 Producing continuous rotation 18 of 26 Boardworks Ltd 2012 Unless the direction of the current is reversed every half turn, the coil will stop rotating. This happens when the current-carrying coil and the lines of force from the permanent magnets are parallel. A device called a commutator is used to momentarily break the circuit and change the direction of the current. This ensures that the coil turns continuously.

When current passes through this, forces act on it.

19 Parts of a motor These provide a permanent magnetic field. axle This reverses the current in the coil to keep it rotating. When current passes through this, forces act on it. Split-ring commutator brushes magnet These provide the connection to the battery. battery coil This allows the coil to spin. This provides the energy source.

of the magnetic field Increase the current flowing

20 To increase the rate at which the motor turns Increase the number of loops Increase the strength of the magnetic field Increase the current flowing through the wire A real motor differs from a loop of wire

Practical Motors The permanent magnets are replaced with curved electromagnets capable of producing very strong magnetic fields The single loop is replaced with several coils of wire wrapped

21 Practical Motors The permanent magnets are replaced with curved electromagnets capable of producing very strong magnetic fields The single loop is replaced with several coils of wire wrapped on the same axis This makes the motor more powerful and allows it to run more smoothly The coils are wrapped on a laminated soft iron core. This makes the motor more efficient and more powerful

22 Energy transfers in motors 22 of 26 Boardworks Ltd 2012 A motor converts electrical energy into useful mechanical energy. Motors are not 100 percent efficient. Some energy is lost as heat energy. electrical mechanical other losses friction resistance

23 Plenary: Multiple-choice quiz 23 of 26 Boardworks Ltd 2012

24 Key words Motor effect - the term used when a current-carrying wire in the presence of a magnetic field experiences a force. Motor a loop of wires spinning around an axle driven by a battery Commutator reverses the current and keeps the coil spinning Brushes provide the connection to the battery Electromagnetism - the interaction of electric currents or fields and magnetic fields. Fleming s left hand rule FBI - F = force on wire, B = external magnetic field, I = current. F = thumb, B is index fg, I = middle fg RHR #3 thumb points in direction of current, flat finger in direction of external field from N to S, force comes out of palm of your hand

KS3 Revision. 8J Magnets and Electromagnets

KS3 Revision. 8J Magnets and Electromagnets KS3 Revision 8J Magnets and Electromagnets 1 of 29 Boardworks Ltd 2007 Contents 8J Magnets and Electromagnets Magnetic materials Magnetic fields Electromagnets Summary activities 2 of 29 Boardworks Ltd