7.10 to 7.12

 

7.10 to 7.12 starter

02 February 2012

10:30

·        Smoke detectors use ²⁴¹Am to emit alpha particles which pass through a small air gap before being detected.  If smoke particles are present they interrupt the beam of alpha particles and this triggers the alarm to go off

·        Tomorrow, will the ²⁴¹Am still be as radioactive?

·        Next year, will the ²⁴¹Am still be as radioactive?

·        In a thousand years, will the ²⁴¹Am still be as radioactive?

Answers

·        To answer the questions, we need to know the half life of Americium-241 which is 432 years

·        Tomorrow and even next year its activity will hardly have changed at all (sensible for a smoke detector - you don't want it to suddenly stop working!)

·        In a thousand years its activity will have dropped to about a quarter

 

 

 

7.10 to 7.12

12 January 2012

10:24

·        7.10 understand that the activity of a radioactive source decreases over a period of time and is measured in becquerels

·        7.11 recall the term ‘half-life’ and understand that it is different for different radioactive isotopes

·        7.12 use the concept of half-life to carry out simple calculations on activity

Half-life of Different Isotopes

·       

<<Half life.pptx>>

<<interactive simple half life calculations.swf>>

<<Decay of Balonium  - exponential graph.swf>>

 

 

7.10 to 7.12 questions

01 February 2012

09:46

1.             What happens to the amount of ‘mother’ nuclei as time passes?

2.             What sort of radioisotope will decay the fastest - one with a long half life or one with a short half life?

3.             Does half life tell us exactly when a particular nucleus in a radioisotope will decay?

4.             What are the two definitions of half life?

5.             What does the activity of a source mean?

6.             What is the unit of activity?

7.             What will happen to the number of ‘mother’ nuclei after two half lives?

8.             What will happen to the activity of a source after two half lives?

 

 

7.10 to 7.12 calculation questions

12 January 2012

10:24

1.  A radioisotope has a half life of 12 years. What fraction of the radioisotope will be left after 60 years?

2.  If the activity of a sample falls to 1/64th of its original level after 2 hours, what is the half life of the sample?

3.  The background radiation in a laboratory is 7 Bq. The count rate from a radioisotope is measured and it has a reading of 119 Bq. If the half life of the radioisotope is 10 minutes, what will be the reading 20 minutes later?

4.  Potassium decays into argon.  The half life of potassium is 1.3 billion years.  A sample of rock from Mars is found to contain three argon atoms for every atom of potassium.  How old is the rock?                                      

interactive simple half life calculations.swf Download this file

Half life.pptx Download this file

Decay of Balonium - exponential graph.swf Download this file

7.6 and 7.7

 

 

7.6 and 7.7

12 January 2012

10:24

·        7.6 describe the effects on the atomic and mass numbers of a nucleus of the emission of each of the three main types of radiation

·        7.7 understand how to complete balanced nuclear equations

<<Balanced nuclear equations.pptx>>

	<<alpha decay of Am241 animation.swf>>
			Did you spot the deliberate mistake on this animation?

<<beta decay of C14 animation.swf>>

Answer

The symbol for Neptunium is Np not NP!

 

 

7.6 and 7.7 Plenary

12 January 2012

10:24

<<interactive alpha and beta decay eqns.swf>>

<<Balanced nuclear equations plenary mulichoice question.pptx>>

interactive alpha and beta decay eqns.swf Download this file

beta decay of C14 animation.swf Download this file

Balanced nuclear equations.pptx Download this file

Balanced nuclear equations plenary mulichoice question.pptx Download this file

alpha decay of Am241 animation.swf Download this file

7.4 and 7.5

 

 

7.4 and 7.5 starter

01 February 2012

10:00

Tell the person next to you…

·        What are the 7 parts of the electromagnetic spectrum you learnt in P3, Waves?

·        What are they in order of increasing frequency?

 

 

<<e-m spec.swf>>

(Note that microwaves are missing from this animation!)

 

 

 

 

 

 

 

 

 

Answers

·   Radio waves

·   Microwaves

·   Infra Red

·   Visible

·   Ultra violet

·   X-Rays

·   Gamma Rays

 

 

7.4 and 7.5

12 January 2012

10:24

·        7.4 understand that alpha and beta particles and gamma rays are ionising radiations emitted from unstable nuclei in a random process

·        7.5 describe the nature of alpha and beta particles and gamma rays and recall that they may be distinguished in terms of penetrating power

Producing Alpha, Beta and Gamma radiation

·       

	<<decays emitting a,b,g.swf>>		<<producing a,b,g.pptx>>

Penetrating Power

·       

·       

	<<penetrating power.swf>>		<<DJFPh107pene3.swf>>

	<<Interactive simulation - penetration of radiation.swf>>		<<DJFPh109gammy5.swf>>

Ionisation

	<<Animation - ionisation of atom by radiation.swf>>		<<DJFPh109ioniz2.swf>>

<<ionisation.pptx>>

Effect of magnetic and electric fields

<<effect of magnetic field on a,b,g.swf>>

<<effect of electric field on a,b,g.swf>>

producing a,b,g.pptx Download this file

penetrating power.swf Download this file

ionisation.pptx Download this file

Interactive simulation - penetration of radiation.swf Download this file

effect of magnetic field on a,b,g.swf Download this file

effect of electric field on a,b,g.swf Download this file

e-m spec.swf Download this file

DJFPh109ioniz2.swf Download this file

DJFPh109gammy5.swf Download this file

DJFPh107pene3.swf Download this file

decays emitting a,b,g.swf Download this file

Animation - ionisation of atom by radiation.swf Download this file

7.9

background radiation.pptx Download this file

 

7.9

12 January 2012

10:24

·        7.9 recall the sources of background radiation

<<background radiation.pptx>>

Whys Guy

·       

7.3

Isotopes.ppt Download this file

7.3

12 January 2012

10:24

·        7.3 understand the terms atomic (proton) number, mass (nucleon) number and isotope

<<Isotopes.ppt>>

 

 

PhET animation - build an atom

31 January 2012

13:34

<<build-an-atom_en.jar>>

Website

http://phet.colorado.edu/en/simulation/build-an-atom

 

Embed code for your blog

<div style="position: relative; width: 300px; height: 226px;">

Click to Run

</div>

 

 

 

PhET animation - isotopes

31 January 2012

13:34

<<isotopes-and-atomic-mass_en.jar>>

Website

http://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass

 

Embed code for your blog

<div style="position: relative; width: 300px; height: 226px;">

Click to Run

</div>

 

7.8

detection of radiation.pptx Download this file

 

7.8

12 January 2012

10:24

·        7.8 understand that ionising radiations can be detected using a photographic film or a Geiger-Muller detector

<<detection of radiation.pptx>>

7.2

 

7.2 starter

31 January 2012

11:35

Tell the person next to you…

·        The names of 3 subatomic particles

·        What properties do they have?

<<atomic structure - electrons orbiting the nucleus.swf>>

<<sub-atomic particles - drag and drop.swf>>

 

 

7.2

11 January 2012

14:49

·        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>>

<<atomic structure of Li - mass and proton numbers.swf>>

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

Proton number and mass number.ppt Download this file

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

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

6.20

 

6.20

01 December 2011

18:08

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

        input power = output power

                     V_p I_p = V_s I_s

<<transformer animation with sliders and example calculations.swf>>

 

 

6.19 and 6.20 Plenary answers

01 December 2011

18:08

a.      V_s/V_p=n_s/n_p

V_s/2=80/20

V_s=8V

 

b.      V_s/V_p=n_s/n_p

V_s/10=20/100

V_s=2V

 

c.       V_s/V_p=n_s/n_p

V_s/240=20/400

V_s=12V

 

d.      V_s/V_p=N_s/N_p

V_s/4=2000/50

V_s=160V

 

2.      V_s/V_p=n_s/n_p

3/24=n_s/480

n_s=60turns

 

a.      Iron  (Why?  Iron is a magnetically soft material - it can be magnetised and lose its magnetism easily.  This is necessary in a transformer as the magnetic field needs to change repeatedly)

b.      electrical energy in the primary coil => magnetic energy in the core =>electrical energy in the secondary coil

c.       dc current produces a steady magnetic field in the core.  To induce a current in the secondary coils there must be a changing magnetic field in the core.

 

a.      Step down (because the voltage decreases)

 

b.      V_s/V_p=n_s/n_p

12/240=n_s/1000

n_s=50turns

 

c.       P = V x I

24 = 12 x I

I = 2A

 

d.      Power in secondary = 24W

 

e.      Power in primary = 24W

 

f. P = V x I

24 = 240 x I

I = 0.1A

 

g.      The current would be greater/double

 

Why?

Efficiency = Useful P_out/Total P_inx100

50 = 24/Total P_in x 100

Total P_in = 48W

 

P = V x I

48 = 240 x I

I = 0.2A

 

 

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

6.19

transformer quick quiz.swf Download this file

 

 

6.19

01 December 2011

18:08

·        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>>

6.17

 

 

6.17

01 December 2011

18:08

·        6.17 recall the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides

 

 

6.17 Practical - model answers

17 January 2012

14:33

·        If you…

·        Turn the powerpack to dc

No current is induced in the Secondary Coil.  To induce current you need a changing magnetic field and this is not produced by applying dc to the Primary Coil

·        Turn the powerpack to ac

ac is induced in the Secondary Coil.  To induce current you need a changing magnetic field and this is produced by applying ac to the Primary Coil

3.   Increase the number of turns in the Secondary Coil

The size of the induced voltage in the secondary coils increases

4.   Increase the voltage on the Primary Coil

The size of the induced voltage in the secondary coils increases

5.   Decrease the number of turns in the Secondary Coil

The size of the induced voltage in the secondary coils decreases

6.   Decrease the voltage on the Primary Coil

The size of the induced voltage in the secondary coils decreases

 

6.16

 

 

6.16

01 December 2011

18:08

·        6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field; also describe the factors which affect the size of the induced voltage

·        Magnet rotating near coil

 

·        Coil rotating near magnet

 

·        ac generator

<<AC Generator animation.swf>>

 

 

 

6.16 Practical - model answers

17 January 2012

14:33

<<faraday_en.jar>>

·        Connect a hand turned generator to a light bulb.  Observe the light bulb when you...

·        Rotate the generator slowly

The induced voltage decreases

·        Rotate the generator quickly

The induced voltage increases

3.  Increase the strength of the magnet

The induced voltage increases

4.  Increase the number of turns in the coil

The induced voltage increases

 

 

6.16 generator simulation

28 November 2011

15:06

Website:

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

 

Embed code for your blog:

 

 

6.16 Plenary

17 January 2012

15:20

·        What are the 3 ways that you can increase the size of the current induced in a generator? 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers

·        Increase the strength of the magnets

·        Increase the speed of the relative motion

·        Use a coil with more turns of wire

AC Generator animation.swf Download this file

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?

<<current induced in a moving wire.swf>>

·        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

		<<current induced in a moving wire.swf>>

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

 

 

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

 

See the full gallery on Posterous

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