HSC Physics. Year 2016 Mark Pages 17 Published Dec 23, Motors and Generators. By Madeline (99.2 ATAR)

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1 HSC Physics Year 2016 Mark Pages 17 Published Dec 23, 2016 Motors and Generators By Madeline (99.2 ATAR)

Powered by TCPDF (www.tcpdf.org) Your notes author, Madeline. Madeline achieved an ATAR of 99.

2 Powered by TCPDF ( Your notes author, Madeline. Madeline achieved an ATAR of 99.2 in 2016 while attending Meriden School Currently studying Bachelor of Engineering Honours (Mechatronic Engineering) and Bachelor of Science (Advanced) at The University of Sydney Achievements: HSC All Rounders 2016 Neighbourhood Engineer's Prize for Physics 2016 Academic Achievement Prize 2016 Prize for Parnassus Mathematics 2016 Madeline says: I am a student that is passionate in the STEM areas. Besides taking Advanced English for my HSC, I also took Mathematics Extension 2, Biology, Chemistry and Physics. I want to share my notes so that other students are able to grasp a full understanding of the course content in a way that is easy to understand.

3 Motors and Generators 1. Motors use the effect of forces on currentcarrying conductors in magnetic fields Discuss the effect on the magnitude of the force on a currentcarrying conductor of variations in: the strength of the magnetic field in which it is located B, F the magnitude of the current in the conductor I, F the length of the conductor in the external magnetic field l, F the angle between the direction of the external magnetic field and the direction of the length of the conductor θ up to 90, F Refer to this formula Use righthand push rule to determine direction Describe qualitatively and quantitatively the force between long parallel currentcarrying conductors: k = constant (2.0x10 7 ) Current in same direction: attract Current in opposite direction: repel Forces due to magnetic field exerted on by the other wire I1/I2, F l, F d, F aka. Ampere s Law Define torque as the turning moment of a force using: Torque = turning force 1

d = distance from pivot to where force is applied Identify that the motor effect is due to the force acting on a currentcarrying conductor in a magnetic field Motor effect from interaction of

currentcarrying loop in a magnetic field and describe the net result of the forces Force acts in opposite direction on opposite sides of coil coil turns Other sides don t experience force bc parallel

4 d = distance from pivot to where force is applied Identify that the motor effect is due to the force acting on a currentcarrying conductor in a magnetic field Motor effect from interaction of magnetic field created by current through conductor and magnetic field from permanent magnets surrounding wire Force produced by interacting magnetic fields Describe the forces experienced by a currentcarrying loop in a magnetic field and describe the net result of the forces Force acts in opposite direction on opposite sides of coil coil turns Other sides don t experience force bc parallel to field At 90, τ = 0, but momentum keeps coil spinning Normal DC motor without commutator: coil will rotate other way bc τ is reversed coil will oscillate about the vertical position bc momentum and inertia is lost (friction), and will eventually come to rest here can use AC current instead (direction changes) Describe the main features of a DC electric motor and the role of each feature Motor: converts electrical energy kinetic energy 2

5 Powered by TCPDF ( Split ring commutator: electrical contact between power source and coil, split breaks circuit every half rotation current running in opposite direction (same direction through other side) continues rotating in same direction Brush: maintains contact with power source, made of graphite (lasts longer than metal) for lubrication + so it doesn t tangle Stator: fixed, stationary magnets (usually radial) provides external magnetic field radial magnets τ, since the coil would be parallel to field in many places could also be electromagnets Armature: frame holding coil Rotor: bit that rotates Identify that the required magnetic field in DC motors can be produced either by currentcarrying coils or permanent magnets Electromagnets: provide stronger magnetic fields, strengths are adjustable, can be turned off and on Can also have radial permanent magnets Solve problems using: Perform a firsthand investigation to demonstrate the motor effect Making motor 1. Coil wire around toilet roll, wrap ends tightly around coil to hold it together, leaving 34cm at the end 2. Remove insulation from ends of wire 3. Use permanent marker to draw over one side of the wire (splitring commutator) 4. Place plastic cup upside down, tape D cell battery on top and bent paperclips on side 5. Tape bar magnet perpendicular to battery 6. Balance coil on paperclips Solve problems and analyse information about the force on currentcarrying conductors in magnetic fields using: Solve problems and analyse information about simple motors using: Motor can be more powerful by: number of coils magnetic field soft iron core enhanced magnetic field external B will enhance B on inside of coil to B through wire Identify data sources, gather and process information to qualitatively describe the application of the motor effect in: the galvanometer Used to measure small amounts of current Basic form of ammeter/voltmeter 3

Note that a current-carrying solenoid produces a dipole field similar to that of a bar magnet. The field is uniform within the coil.

Note that a current-carrying solenoid produces a dipole field similar to that of a bar magnet. The field is uniform within the coil. An electrical current produces a magnetic field that is directed around it. Conventional current is the flow of positive charge. Hence, it is directed from the positive terminal of the power supply, through