Rohan IGCSE Physics http://rohanigcsephysics.posterous.com Most recent posts at Rohan IGCSE Physics posterous.com Wed, 16 May 2012 20:10:03 -0700 Untitled http://rohanigcsephysics.posterous.com/131263474 http://rohanigcsephysics.posterous.com/131263474

Homework for next Tuesday

1.    4.6 to 4.8 Reading from Pearson.  Note down 5 key facts from the text in your exercise books as 5 bullet points – I will check these at the beginning of next lesson.  Stuck?  Use Objectives 4.6 to 4.8 to guide you as to what you need to know.

2.    Rate yourself using A/T/W/U against objectives 4.6 to 4.8 in the “End of lesson” column

Image001

 

4.6 to 4.8 Reading from Pearson

10 May 2012

14:41

 

 

4.2 to 4.5 Plenary Answers, Pearson p.132

10 May 2012

08:54

Image001

b.

Efficiency = Useful Eout / Total Ein x 100

Efficiency = 350 / 400 x 100

Efficiency = 88%

 

Image002

a.               It is transferred to thermal and sound energy

 

 

4.2 to 4.5 Plenary Questions, Pearson p.132

10 May 2012

08:54

0image001

 

 

 

 

 

4.5

10 June 2011

11:42

·         4.5 describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship (see 4.4), including their representation by Sankey diagrams

1image001

 

 

4.5 plenary questions and answers

10 June 2011

11:42

0image002

Answers

 

Kettle

10 squares = 2000J/s therefore 1 square = 200J/s

Wasted Heat = 2 squares = 400J/s

Useful Heat = 5 squares = 1000J/s

Wasted sound = 3 squares = 600J/s

 

Efficiency = Useful Eout / Total Ein x 100

Efficiency = 1000 / 2000 x 100

Efficiency = 50%

 

Computer

Conservation of energy so…

Total Ein = Total Eout

150J = 20 + 10 + Useful Eout

Useful Eout = 120J/s

 

Efficiency = Useful Eout / Total Ein x 100

Efficiency = 120 / 150 x 100

Efficiency = 80%

 

 

4.4

10 June 2011

11:42

·         4.4 know and use the relationship:

                             efficiency = Useful Eout / Total Ein

Version 1

 

Efficiency = Useful Eout / Total Ein x 100

 

Useful Eout = useful energy output (J)

Total Ein = total energy input (J)

Efficiency = Efficiency (%)

 

Version 2

 

Efficiency = Useful Eout / Total Ein

 

Useful Eout = useful energy output (J)

Total Ein = total energy input (J)

Efficiency = Efficiency (no units; a number between 0 and 1)

 

 

4.4 Plenary questions

10 June 2011

11:42

<<Efficiency.ppt>>

Efficiency.ppt Download this file

 

 

4.4 starter

10 June 2011

11:42

<<% efficiency energy.swf>>

% efficiency energy.swf Download this file

 

 

4.3

10 June 2011

11:42

•        4.3 understand that energy is conserved

<<Energy input; energy output worksheets.pdf>>

2image001

Example answer

1image002

Energy input; energy output worksheets.pdf Download this file

 

 

4.2 starter

10 June 2011

15:32

Tell the person next to you…

1.             What are the 9 types of energy?

(Note: "solar", "wind", etc are NOT types of energy - they are energy resources!)

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Wed, 09 May 2012 20:38:49 -0700 Do you know your formulae? http://rohanigcsephysics.posterous.com/do-you-know-your-formulae http://rohanigcsephysics.posterous.com/do-you-know-your-formulae

 

Do you know your formulae?

28 February 2011

07:14

Unit 3 Formulae

 

Tell the person next to you…

·         All of the formulae from this unit

o    eg. "The formula that links v, f and λ is…"

·         All of the quantities from this unit

o    eg. "λ = Wavelength"

·         All of the units from this unit

o    eg. "The unit of wavelength is metres"

Answers

 

Formulae

 

·         v = f x λ

·         f = 1/T

·         n = sin i / sin r

·         sin c = 1/n

·         v = d / t

 

Quantities and Units

 

·         v = wave speed (m/s)

·         f = frequency (Hertz, Hz)

·         λ = wavelength (m)

·         T = period (s)

·         n = refractive index (no units)

·         i = angle of incidence (o)

·         r = angle of refraction (o)

·         c = critical angle (o)

·         d = distance (m)

·         t = time (s)

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Wed, 09 May 2012 20:38:30 -0700 3.25 http://rohanigcsephysics.posterous.com/325 http://rohanigcsephysics.posterous.com/325

 

 

3.25

10 February 2011

14:49

·         3.25 describe how digital signals can carry more information

 

 

Vinyl LP record - old school!

DVD

 

 

 

 

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Wed, 09 May 2012 20:38:20 -0700 3.24 http://rohanigcsephysics.posterous.com/324 http://rohanigcsephysics.posterous.com/324

 

3.24

10 February 2011

14:56

·         3.24 describe the advantages of using digital signals rather than analogue signals

Image001

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Wed, 09 May 2012 20:38:02 -0700 3.23 http://rohanigcsephysics.posterous.com/323 http://rohanigcsephysics.posterous.com/323

3.23

10 February 2011

14:56

·         3.23 understand the difference between analogue and digital signals

Image001

·         Analogue signals vary continuously

·         Digital signals are discrete - they are either 1 (on) or 0 (off)

·         Data stored as a stream of 1s and 0s is called "binary code"

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Tue, 03 Apr 2012 20:57:48 -0700 Untitled http://rohanigcsephysics.posterous.com/118833565 http://rohanigcsephysics.posterous.com/118833565

 

 

3.20

10 February 2011

14:56

·         3.20 describe the role of total internal reflection in transmitting information along optical fibres and in prisms

 

 

<<Total internal reflection.mpg>>

 

TIR

Optical fibres

 

<<TIR demo and uses of - interactive.swf>>

Applications of TIR using prisms

Periscope

Image001

 

Bicycle reflector

Image002

 

Binoculars

Image003

 

Applications of TIR using fibre optics

Endoscope

Image004

 

Communications networks (telephone and internet)

Image005

TIR demo and uses of - interactive.swf Download this file

Plenary Questions.pptx Download this file

 

 

3.21

10 February 2011

14:56

·         3.21 explain the meaning of critical angle c

 

 

·         You should already have learnt this from the keywords from this unit

·         Tell the person next to you the definition now!

 

 

 

 

 

 

 

 

 

 

Answer

·         The smallest angle of incidence for which Total Internal Reflection occurs

also acceptable:

·         The angle of incidence for which the angle of refraction is exactly 90o

 

 

3.22

10 February 2011

14:56

·         3.22 know and use the relationship between critical angle, and refractive index:

              sin c = 1 / n

sin c = 1 / n

 

c = critical angle (o)

n = refractive index (no units)

 

 

3.22 Plenary Answers

09 March 2012

09:46

Answers

Q1.  What is the refractive index of glass that has a critical angle of 42o?

 

sin c = 1/n

sin 42 = 1/n

n = 1/sin 42

n = 1.5

 

Q2.  What is the critical angle for diamond? (ndiamond = 2.4)

 

sin c = 1/n

sin c = 1/2.4

c = sin-1 0.417

c = 25o

 

 

3.14 to 3.22 Plenary questions, Pearson p.116 and 117

21 March 2012

12:57

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Mon, 12 Mar 2012 22:09:31 -0700 Untitled http://rohanigcsephysics.posterous.com/110608172 http://rohanigcsephysics.posterous.com/110608172

 

 

3.14

10 February 2011

14:45

·         3.14 recall that light waves are transverse waves which can be reflected, refracted and diffracted

 

Watch the demos for...

·         Reflection of a laser in a smoke box

·         Refraction of a laser in a smoke box

·         Diffraction of a laser by a human hair

 

 

3.10 to 3.13 Plenary Answers

01 April 2011

16:09

<<Answers to Everything I need to know about the EM Spectrum.doc>>

Answers to Everything I need to know about the EM Spectrum.doc Download this file

 

 

3.15 practical

10 February 2011

14:56

<<Investigating reflection expt worksheet.doc>>

 

 

3.15

10 February 2011

14:56

·         3.15 recall that the angle of incidence equals the angle of reflection

Reflection, i=r

<<Obj 3.15.ppt>>

<<animated law of reflection.swf>>

 

 

3.15 plenary

10 February 2011

14:56

<<reflection game.swf>>

reflection game.swf Download this file

Obj 3.15.ppt Download this file

Investigating reflection expt worksheet.doc Download this file

animated law of reflection.swf Download this file

 

 

3.16

10 February 2011

14:56

·         3.16 construct ray diagrams to illustrate the formation of a virtual image in a plane mirror

<<Obj 3.16.ppt>>

Reflection – virtual image

 

 

3.16 Plenary Answers

10 February 2011

14:56

For plane mirrors, the image is…

·         The same size as the object

·         The same distance as the object from the mirror

·         Virtual (not real)

·         Upright

·         Laterally Inverted

Task 1 Answers

 

For plane mirrors, the image is…

·         The same size as the object

·         The same distance as the object from the mirror

·         Virtual (not real)

·         Upright

·         Laterally Inverted

 

 

3.15 and 3.16 Plenary Multiple Choice Questions

21 April 2011

09:44

<<Plenary Questions.ppt>>

Plenary Questions.ppt Download this file

Obj 3.16.ppt Download this file

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Tue, 28 Feb 2012 22:28:37 -0800 Untitled http://rohanigcsephysics.posterous.com/106191701 http://rohanigcsephysics.posterous.com/106191701

 

 

3.9

10 February 2011

14:52

·         3.9 understand that waves can be diffracted through gaps, and that the extent of diffraction depends on the wavelength and the physical dimension of the gap

 

Diffraction by a gap

·         Most of the wave passes straight through the gap

·         But the sea wall causes diffraction at the edges of the wave

·         Note that the wavelength is the same before and after diffraction

Image001

 

·         Diffraction is at a maximum when the width of the gap is equal to the wavelength of the wave

·         The plane waves are now completely curved

·         Note that the wavelength is the same before and after diffraction

Image002

 

Website http://www.falstad.com/ripple/

Image003

 

Diffraction patterns in the sea

 

 

 

3.9 Plenary Answers

10 February 2011

14:52

PFY p.178 Q.2

Image006

 

 

3.8

10 February 2011

14:52

·         3.8 understand that waves can be diffracted when they pass an edge

 

Website http://www.falstad.com/ripple/

0image001

 

 

 

3.10 and 3.11 starter

27 February 2012

15:17

·         Do you know the 7 colours of the visible spectrum?

·         Can you put them in order from longest to shortest wavelength?

Answer

1.            Red (longest wavelength)

2.            Orange

3.            Yellow

4.            Green

5.            Blue

6.            Indigo

7.            Violet (shortest wavelength)

 

How can you remember the order?

Richard Of York Gave Battle In Vain!

 

 

3.10 and 3.11 starter 2

27 February 2012

15:17

·         Do you know the 7 parts of the EM spectrum?

·         Can you put them in order from longest to shortest wavelength?

Answer

1.              Radio (longest wavelength)

2.              Microwaves

3.              Infrared

4.              Visible

5.              Ultraviolet

6.              X-rays

7.              Gamma rays (shortest wavelength)

 

Can you make a mnemonic to help you remember the order?

by Remembering Mnemonics I ...

 

 

3.10 and 3.11

10 February 2011

14:44

·         3.10 understand that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations and that all these waves travel at the same speed in free space

·         3.11 recall the order of the electromagnetic spectrum in decreasing wavelength and increasing frequency, including the colours of the visible spectrum

EM Spectrum – speed, wavelength and frequencies

<<EMFlash[1].swf>>

 

 

3.10 and 3.11 plenary

10 February 2011

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Tue, 21 Feb 2012 20:32:45 -0800 3.5 http://rohanigcsephysics.posterous.com/35 http://rohanigcsephysics.posterous.com/35

3.5 recall and use the relationship between the speed, frequency and wavelength of a wave:          

    wave speed = frequency × wavelength           

                   v = f × λ

 

 

<<Waves - Tr Lo WL f A.mpg>>

<<Longitudinal wave, wavelength. v = f x lambda.mpg>>

 

v = f λ

v = wave speed (m/s)

f = frequency (Hz) or (cycles/s)

λ = wavelength (m)

 

1,000 Hz = 1 kHz 

1000,000 Hz = 1,000 kHz = 1 MHz

 

 

3.5 Plenary

10 February 2011

14:52

·         What happens to the wavelength if you increase the frequency of the wave but keep the wave speed the same?

·         What happens to the wavelength if you decrease the frequency of the wave but keep the wave speed the same?

·         Verify your answers by using http://www.falstad.com/ripple/

 

Super tough extension task

·         Try changing the speed in the simulation.  Does that do what you expect?  Explain.

Answers

v = f λ

Image001

Increases

v = f λ

Image002

Decreases

Super tough extension task

·         Try changing the speed in the simulation.  Does that do what you expect?  Explain.

·         The slider just changes the "simulation speed" NOT the "wave speed"!

 

 

virtual ripple tank

11 January 2011

15:12

Link to animation

http://www.falstad.com/ripple/

 

Embed code for your blog

Longitudinal wave, wavelength. v = f x lambda.mpg Watch on Posterous

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Tue, 21 Feb 2012 20:31:25 -0800 Answers to PFY p.178 http://rohanigcsephysics.posterous.com/answers-to-pfy-p178 http://rohanigcsephysics.posterous.com/answers-to-pfy-p178

 

3.7 Answers

10 February 2011

14:52

PFY p.178 Answers

Image001

v = f λ

v = 170 x 2

v = 340m/s

 

Image002

v = f λ

v = 200,000 x 1,500

v = 300,000,000m/s

 

v = f λ

300,000,000 = 500,000 x λ

λ = 600m

 

Image003

f = 1 / T

2 = 1 / T

T = 0.5s

 

Image004

·         5 complete cycles of the wave measures 10cm

·         So each cycles measures 10cm/5 = 2cm

·         Therefore λ = 2cm or 0.02m

 

v = f λ

6cm/s = f x 2cm

f = 3Hz

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Tue, 21 Feb 2012 20:30:56 -0800 3.6 http://rohanigcsephysics.posterous.com/36 http://rohanigcsephysics.posterous.com/36

·         3.6 use the relationship between frequency and time period:

      frequency =        1                 f = 1       

                        time period               T

f = 1/T

f = frequency (Hz) or (cycles/s)

T = period (the time for one cycle) (s)

<<f=1overT.ppt>>

<<f=1overT drag and drop questions.swf>>

f=1overT.ppt Download this file

f=1overT drag and drop questions.swf Download this file

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Tue, 21 Feb 2012 20:30:54 -0800 3.4 http://rohanigcsephysics.posterous.com/34 http://rohanigcsephysics.posterous.com/34

·         3.4 recall that waves transfer energy and information without transferring matter

<<Energy transfer in waves.ppt>>

 

 

3.4 Plenary Answer

10 February 2011

14:52

Answer 1

Image001

Answer 2

Image002

But NOT both!

Energy transfer in waves.ppt Download this file

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Tue, 21 Feb 2012 20:30:29 -0800 3.7 http://rohanigcsephysics.posterous.com/37 http://rohanigcsephysics.posterous.com/37

·         3.7 use the above relationships in different contexts including sound waves and electromagnetic waves

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Tue, 21 Feb 2012 20:29:09 -0800 3.2 http://rohanigcsephysics.posterous.com/32 http://rohanigcsephysics.posterous.com/32

·         3.2 describe longitudinal and transverse waves in ropes, springs and water where appropriate

Transverse Waves

·        

<<transverse wave - perpendicular motion.swf>>

Longitudinal Waves

·          

<<longitudinal waves - same direction of motion.swf>>

 

 

3.2 Practicals

10 February 2011

14:44

Practicals:

·         Make a transverse wave on a rope

·         Make a longitudinal wave on a rope

(commendations available for anyone who can do this!)

·         Make a transverse wave on a slinky spring

·         Make a longitudinal wave on a slinky spring

·         Observe a transverse wave on a ripple tank

 

 

3.2 Plenary Answers 1

10 February 2011

14:44

Answers

 

Transverse

Longitudinal

Radio

Sound

Microwaves

Spring

Infrared

 

Light

 

Ultraviolet

 

X-rays

 

Gamma rays

 

Water

 

Rope

 

Spring

 

 

 

3.2 Plenary Answers 2

10 February 2011

14:44

PFY p.178

Image001

transverse wave - perpendicular motion.swf Download this file

longitudinal waves - same direction of motion.swf Download this file

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Mon, 06 Feb 2012 20:37:00 -0800 Untitled http://rohanigcsephysics.posterous.com/99610748 http://rohanigcsephysics.posterous.com/99610748

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Mon, 23 Jan 2012 20:48:03 -0800 Untitled http://rohanigcsephysics.posterous.com/95810073 http://rohanigcsephysics.posterous.com/95810073

 

 

2.19

24 November 2010

10:32

·         2.19 recall that:

·         voltage is the energy transferred per unit charge passed

·         the volt is a joule per coulomb.

V = E/Q or E = Q.V

V = Voltage (V)

E = Energy (J)

Q = Charge (C)

 

Therefore 1V = 1J/C

 

 

2.19 Top Tips for Calculations

24 November 2010

10:32

Top Tips for Calculations

(The bold writing is what you write down)

1.              Write down what the question tells you.  I = 4A, t = 20s

2.              Write down what the question asks you for.  Q = ?

3.              Find an equation that links all these variable. 

Formula  Q = I.t                    (1 mark)

4.              Substitution  Q = 4 x 20        (1 mark)

5.              Answer and Units Q = 80C     (1 mark)

 

 

2.17 and 2.19 Plenary worksheet

15 December 2011

09:30

<<Q=It and V=EoverQ worksheet.doc>>

Image001

Q=It and V=EoverQ worksheet.doc Download this file

 

 

2.17

24 November 2010

10:31

·         2.17 recall and use the relationship between charge, current and time:

        charge = current × time     

               Q = I × t

Q = I.t

Q = Charge (C, Coulomb)

I = Current (A)

t = time (s)

 

How to remember this formula…

"If the exam is hard, don't ever Q(u)It"

 

 

2.16

24 November 2010

10:31

·         2.16 understand that current is the rate of flow of charge

Demo

·         Ball of aluminium foil swinging between two metal plates which are charged by Wimshurst generator

·        

 

 

2.18 answers

24 November 2010

10:32

·         2.18 recall that electric current in solid metallic conductors is a flow of negatively charged electrons

Conventional  Current

·         The flow of "imaginary" positive charges from + to -

·         Why?  Positive charges are repelled by the positive terminal of the battery and attracted to the negative terminal of the battery

·         Symbol "I"

·         Used in 90% of exam questions!

 

 

I

I

I

0image001

Flow of Electrons

·         The flow of real negatively charged electrons from - to +

·         Why?  Negative electrons are repelled by the negative terminal of the battery and attracted to the positive terminal of the battery

 

Image002

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Sat, 21 Jan 2012 22:58:39 -0800 2.11 Exam style question - model answer http://rohanigcsephysics.posterous.com/211-exam-style-question-model-answer http://rohanigcsephysics.posterous.com/211-exam-style-question-model-answer 2.11 Exam style question - model answer

26 November 2010

12:43
[cid:image001.jpg@01CCD50F.43F028A0]
· Explain the shape of the V-I graph for a filament lamp with reference to the movement of electrons in the tungsten wire and the temperature of the wire (3 marks)
[cid:image002.png@01CCD50F.43F028A0]

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Sat, 21 Jan 2012 22:58:12 -0800 2.14 http://rohanigcsephysics.posterous.com/214 http://rohanigcsephysics.posterous.com/214 2.14

24 November 2010

10:16
· 2.14 know that lamps and LEDs can be used to indicate the presence of a current in a circuit
>

Crocodile technology
· Drag file 6 (attached) into the Croc clips window and it will open (you might have to save this file to your desktop first)
· Push the push switches on each of the 4 circuits
· Can you explain what you see?

2.14 answers

24 November 2010

10:16

Filament lamps
· Turn on when a current flows either way through them
· You can see that their V/I graph is symmetrical - they behave the same with positive and negative voltages

[cid:image001.jpg@01CCD50B.40EAD4B0]

Light Emitting Diodes (LEDs)
· Turn on when a current flows "forwards" through them (in the direction of the arrow)
· You can see that their V/I graph is asymmetric - they behave differently with positive and negative voltages
· Diodes are like a one way door that
o allows current to flow when a positive voltage is applied
o does not allow current to flow when a negative voltage is applied

[cid:image002.png@01CCD50B.40EAD4B0]

6 LEDs vs lamps.cyt Download this file

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Sat, 21 Jan 2012 22:57:22 -0800 2.13 plenary MABA http://rohanigcsephysics.posterous.com/213-plenary-maba http://rohanigcsephysics.posterous.com/213-plenary-maba 2.13 plenary MABA

24 November 2010

10:15
· 2.13 describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature

LDR


Light


Dark (4 letters)


Resistance (high/low)


Low


High (4 letters)


Thermistor


Hot (3 letters)


Cold (4 letters)


Resistance (high/low)


Low (3 letters)


High (4 letters)

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Sat, 21 Jan 2012 22:53:46 -0800 2.13 practical http://rohanigcsephysics.posterous.com/213-practical http://rohanigcsephysics.posterous.com/213-practical 2.13 practical

24 November 2010

10:15
· 2.13 describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature
· Select the 20kΩ range on the multimeter
· Connect an LDR to the multimeter
· Use your thumb to cover the LDR
· Connect a thermistor to the multimeter
· Rub the thermistor between your finger and thumb to warm it up
· Fill in the following results tables

LDR


Light


Dark


Resistance (kΩ)


Resistance (high/low)


Thermistor


Hot


Cold


Resistance (kΩ)


Resistance (high/low)

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http://posterous.com/images/profile/missing-user-75.png http://posterous.com/users/hdojw5lzF65Sy Rohan Rohan Rohan