Faraday's Lab animation 28 November 2011 15:06 > Website: http://phet.colorado.edu/en/simulation/faraday 6.16 generator simulation 28 November 2011 15:06 Website: http://www.walter-fendt.de/ph14e/generator_e.htm
Friday, 3 February 2012
6.15
6.15 starter 01 December 2011 18:08
· What’s the motor effect?
· "If there’s a magnetic field perpendicular to a current in a wire, the wire moves in a direction perpendicular to the field and the current" (FLHR)
· So what about if we move a wire in a magnetic field? What happens in the wire?
>
· When we move a wire in a magnetic field, a current is induced in the wire 6.15 01 December 2011 18:08
· 6.15 recall that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it; also recall the factors which affect the size of the induced voltage
[cid:image001.png@01CCE252.11AB81F0] [cid:image002.jpg@01CCE252.11AB81F0] >
> 6.15 Practical - model answers 17 January 2012 14:33
· If you...
· Push the North pole of the magnet into the coil A negative current flow shown by a negative deflection on the ammeter
· Keep the magnet stationary within the coil No current
3. Pull the North pole of the magnet out of the coil A positive current
4. Push the South pole of the magnet into the coil A positive current
5. Push the North pole of the magnet slowly into the coil A smaller negative current
6. Push the North pole of the magnet quickly into the coil A larger negative current
7. Change the coil for one with more turns of wire and push the North pole of the magnet into the coil A larger negative current
8. Push the North pole of a neodymium (strong) magnet into the coil A larger negative current
9. Move the magnet in and out of the coil repeatedly. What sort of current is this? An alternating current 6.15 Plenary answers 16 January 2012
· Explain carefully how you can induce a current in a wire (3 marks)
· State 3 ways you can increase the size of this induced current (3 marks) Answers
· The wire must be perpendicular to a magnetic field
· The wire and magnetic field must move relative to each other – the wire must “cut” through the magnetic field lines/lines of magnetic flux as it moves
· A current is induced in the wire. The induced current is perpendicular to both the field and the motion
· Increase the strength of the magnets
· Increase the speed of the relative motion
· Use a coil of wire instead of a single piece of wire 
· What’s the motor effect?
· "If there’s a magnetic field perpendicular to a current in a wire, the wire moves in a direction perpendicular to the field and the current" (FLHR)
· So what about if we move a wire in a magnetic field? What happens in the wire?
>
· When we move a wire in a magnetic field, a current is induced in the wire 6.15 01 December 2011 18:08
· 6.15 recall that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it; also recall the factors which affect the size of the induced voltage
[cid:image001.png@01CCE252.11AB81F0] [cid:image002.jpg@01CCE252.11AB81F0] >
> 6.15 Practical - model answers 17 January 2012 14:33
· If you...
· Push the North pole of the magnet into the coil A negative current flow shown by a negative deflection on the ammeter
· Keep the magnet stationary within the coil No current
3. Pull the North pole of the magnet out of the coil A positive current
4. Push the South pole of the magnet into the coil A positive current
5. Push the North pole of the magnet slowly into the coil A smaller negative current
6. Push the North pole of the magnet quickly into the coil A larger negative current
7. Change the coil for one with more turns of wire and push the North pole of the magnet into the coil A larger negative current
8. Push the North pole of a neodymium (strong) magnet into the coil A larger negative current
9. Move the magnet in and out of the coil repeatedly. What sort of current is this? An alternating current 6.15 Plenary answers 16 January 2012
· Explain carefully how you can induce a current in a wire (3 marks)
· State 3 ways you can increase the size of this induced current (3 marks) Answers
· The wire must be perpendicular to a magnetic field
· The wire and magnetic field must move relative to each other – the wire must “cut” through the magnetic field lines/lines of magnetic flux as it moves
· A current is induced in the wire. The induced current is perpendicular to both the field and the motion
· Increase the strength of the magnets
· Increase the speed of the relative motion
· Use a coil of wire instead of a single piece of wire
Wednesday, 1 February 2012
6.14
6.14
01 December 2011 18:05· 6.14 recall that the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with the current
> Exam style question
· What changes can you make to a simple dc motor to increase the force it can exert? (3 marks) Model Answer
· Increase the strength of the magnetic field
· Increase the current in the coil
· Increase the number of turns on the coil
6.11 to 6.14 Plenary answers
6.11 to 6.14 Plenary answers
[cid:image001.png@01CCE0EC.B3A28CE0]
1. Magnetic Field is N to S (down the page) = First finger
2. Current is to the left = seCond finger
3. Motion is out of the page = ThuMb
Tuesday, 31 January 2012
6.13
6.13 starter 12 December 2011 16:07 Practical - the current balance
· Use a current balance to investigate what happens when a current flows in a magnetic field
· How many magnetic fields are created by this apparatus?
· How could you make the wire move further? (2 ways)
· How could you change the direction the wire moves in? (2 ways)
> Answers
1. 2 magnetic fields:
a. the uniform magnetic field created between the poles of the permanent magnet
b. the magnetic field around the wire when the current flows
2.
a. Increase the current in the wire
b. Increase the strength of the magnetic field
3.
a. Reverse the poles of the magnets
b. Reverse the direction of the current 6.13 01 December 2011 18:05
· 6.13 use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
[cid:image001.png@01CCE0EB.1DF42E20]
> 6.13 FLHR simulation 28 November 2011 15:06 Website: http://www.walter-fendt.de/ph14e/lorentzforce.htm Embed code for your blog: Example: http://maddog11physics.posterous.com/68-field-around-current-carrying-conduct... 6.13 Plenary 12 December 2011 11:55
> 
· Use a current balance to investigate what happens when a current flows in a magnetic field
· How many magnetic fields are created by this apparatus?
· How could you make the wire move further? (2 ways)
· How could you change the direction the wire moves in? (2 ways)
> Answers
1. 2 magnetic fields:
a. the uniform magnetic field created between the poles of the permanent magnet
b. the magnetic field around the wire when the current flows
2.
a. Increase the current in the wire
b. Increase the strength of the magnetic field
3.
a. Reverse the poles of the magnets
b. Reverse the direction of the current 6.13 01 December 2011 18:05
· 6.13 use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
[cid:image001.png@01CCE0EB.1DF42E20]
> 6.13 FLHR simulation 28 November 2011 15:06 Website: http://www.walter-fendt.de/ph14e/lorentzforce.htm Embed code for your blog: Example: http://maddog11physics.posterous.com/68-field-around-current-carrying-conduct... 6.13 Plenary 12 December 2011 11:55
>
6.12
6.12 01 December 2011 18:05
· 6.12 recall that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers 6.12 Practical - dc motor 12 December 2011 15:29
· Connect a dc motor to a power pack
· How you can reverse the direction of spin of the motor? (2 ways)
· How you can make a stronger turning force on the motor? (2 ways)
3. How can you see that the turning force is stronger? Answers
1.
a. Reverse the poles of the magnets
b. Reverse the direction of the current in the coil by switching over the polarity of the wires to the power pack
2.
a. Increase the current in the wire (by increasing the voltage of the power pack)
b. Increase the strength of the magnetic field (by adding more magnets to the yoke)
3. The motor spins faster which indicates a larger turning force 6.12 dc motor simulation 28 November 2011 15:06 Website: http://www.walter-fendt.de/ph14e/electricmotor.htm Embed code for your blog: 6.12 loudspeakers 12 December 2011 15:37
> >
Exam style question
· Explain carefully how an alternating current in the coil of a loudspeaker can create a sound (4 marks)
[cid:image001.jpg@01CCE0EB.29C58A50] Gapfill Model Answer
· When a ______ flows __ the ____, it is p____________ to the magnetic field
· This creates a ______ on the coil, due to ___ _____ effect, and so the coil _____
· When the _________ current reverses ______, the direction of the _______ is also reversed and the coil moves in the ________ direction
· The moving ____ is attached to a ____ which also moves __________ and forwards.
· This makes ___ ________ vibrate and this is the _____ we can hear Model Answer Any four points from...
· When a current flows in the coil, it is perpendicular to the magnetic field
· This creates a force on the coil, due to the motor effect, and so the coil moves
· When the alternating current reverses direction, the direction of the force is also reversed and the coil moves in the opposite direction
· The moving coil is attached to a cone which also moves backwards and forwards.
· This makes air particles vibrate and this is the sound we can hear 
· 6.12 recall that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers 6.12 Practical - dc motor 12 December 2011 15:29
· Connect a dc motor to a power pack
· How you can reverse the direction of spin of the motor? (2 ways)
· How you can make a stronger turning force on the motor? (2 ways)
3. How can you see that the turning force is stronger? Answers
1.
a. Reverse the poles of the magnets
b. Reverse the direction of the current in the coil by switching over the polarity of the wires to the power pack
2.
a. Increase the current in the wire (by increasing the voltage of the power pack)
b. Increase the strength of the magnetic field (by adding more magnets to the yoke)
3. The motor spins faster which indicates a larger turning force 6.12 dc motor simulation 28 November 2011 15:06 Website: http://www.walter-fendt.de/ph14e/electricmotor.htm Embed code for your blog: 6.12 loudspeakers 12 December 2011 15:37
> >
Exam style question
· Explain carefully how an alternating current in the coil of a loudspeaker can create a sound (4 marks)
[cid:image001.jpg@01CCE0EB.29C58A50] Gapfill Model Answer
· When a ______ flows __ the ____, it is p____________ to the magnetic field
· This creates a ______ on the coil, due to ___ _____ effect, and so the coil _____
· When the _________ current reverses ______, the direction of the _______ is also reversed and the coil moves in the ________ direction
· The moving ____ is attached to a ____ which also moves __________ and forwards.
· This makes ___ ________ vibrate and this is the _____ we can hear Model Answer Any four points from...
· When a current flows in the coil, it is perpendicular to the magnetic field
· This creates a force on the coil, due to the motor effect, and so the coil moves
· When the alternating current reverses direction, the direction of the force is also reversed and the coil moves in the opposite direction
· The moving coil is attached to a cone which also moves backwards and forwards.
· This makes air particles vibrate and this is the sound we can hear
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