7.2

Tell the person next to you…

·         The names of 3 subatomic particles

·         What properties do they have?

atomic structure - electrons orbiting the nucleus.swf Download this file

sub-atomic particles - drag and drop.swf Download this file

·         7.2 describe the structure of an atom in terms of protons, neutrons and electrons and use symbols such as ¹⁴₆C to describe particular nuclei

Proton number and mass number.ppt Download this file

atomic structure of Li - mass and proton numbers.swf Download this file

P7 student objectives sheet

P7 IGCSE Physics Student Objectives.doc Download this file

P7 student objectives sheet

P7 IGCSE Physics Student Objectives.doc Download this file

6.18

6.18 explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy

·   

National grid worksheet.doc Download this file

6.20

6.20 recall and use the relationship (for 100% efficiency):

        input power = output power

                     V_p I_p = V_s I_s

 

6.19 and 6.20 Plenary

transformer worksheet.doc Download this file

transformer animation with sliders and example calculations.swf Download this file

6.19

6.19 recall and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer:

input (primary) voltage        = primary turns

output (secondary) voltage     secondary turns

                                          V_p/V_s = n_p/n_s

transformer quick quiz.swf Download this file

6.17

6.17.docx Download this file

6.16

6.16.docx Download this file

AC Generator animation.swf Download this file

Faraday's Lab animation

Faraday's Lab animation

Website:

http://phet.colorado.edu/en/simulation/faraday

 

6.16 generator simulation

Website:

http://www.walter-fendt.de/ph14e/generator_e.htm

6.15

6.15.docx Download this file

induction - magnet moving into coil (slow, fast, poles reversed).swf Download this file

current induced in a moving wire_2.swf Download this file

current induced in a moving wire.swf Download this file

6.15

What’s the motor effect?

"If there’s a magnetic field perpendicular to acurrent 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 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

<<induction - magnet moving into coil (slow, fast, poles reversed).swf>>

6.15 Practical - model answers

·         

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

·         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

 

induction - magnet moving into coil (slow, fast, poles reversed).swf Download this file

current induced in a moving wire_2.swf Download this file

current induced in a moving wire.swf Download this file

6.8 to 6.10 Plenary answers

See the full gallery on Posterous

6.8 to 6.10 Plenary answers

See the full gallery on Posterous

6.11

·         

6.11 appreciate that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

Solar wind creating aurora animation

Timelapse of aurora

 

6.14

·         

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

<<dc motor - factors affecting the speed of a motor interactive.swf>>

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

dc motor - factors affecting the speed of a motor interactive.swf Download this file

6.12

·         

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:

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6.12 loudspeakers

12 December 2011

15:37

	<<Loudspeaker demo with voice over.swf>>		<<animated loudspeaker - slow and clear.swf>>

Exam style question

·         Explain carefully how an alternating current in the coil of a loudspeaker can create a sound (4 marks)

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

Loudspeaker demo with voice over.swf Download this file

animated loudspeaker - slow and clear.swf Download this file

6.13

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

<<FLHR practice.pptm>>

6.13 FLHR simulation

28 November 2011

15:06

Website:

http://www.walter-fendt.de/ph14e/lorentzforce.htm

6.13 Plenary

12 December 2011

11:55

<<FLHR Animation - Force on current carrying wire.swf>>

Magnetic fields interacting - Force on current carrying wire.swf Download this file

FLHR practice.pptm Download this file

FLHR Animation - Force on current carrying wire.swf Download this file

6.13

Untitled

6.8 to 6.10 Plenary answers

See the full gallery on Posterous

6.10

·         

6.10 sketch and recognise magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current

Straight wire = Right hand grip rule

Flat circular coil

Solenoid

6.8 to 6.10 Plenary questions

6.8

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