Seb Physics

Tuesday, 13 March 2012

7.15 and 7.16 Plenary Answers

12 January 2012

10:24

1. How are alpha particles deflected by the "Plum Pudding Model"

The alpha particles are not deflected - they pass straight through

2. How are alpha particles deflected by "Rutherford's Nuclear Model"

· Most alpha particles are undeflected and pass straight through

· Some alpha particles are deflected through a small angle

· A few alpha particles are deflected through a large angle

· What happens if you increase the speed of the alpha particles?

The amount of deflection decreases as the alpha particles have more Kinetic Energy to overcome a greater amount of Electrostatic Potential Energy of their repulsion with the nucleus.

4. What happens if you increase the charge of the nucleus?

The amount of deflection increases as there is now greater electrostatic repulsion between the nucleus and the alpha particle

5. What happens if you increase the number of neutrons in the nucleus?

The amount of deflection is unaffected (increasing the number of neutrons does not affect the charge on the nucleus)

Thursday, 2 February 2012

6.18

National grid worksheet.doc Download this file

6.18

01 December 2011

18:08

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

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

01 December 2011

18:08

<<transformer worksheet.doc>>

transformer worksheet.doc Download this file

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

· 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 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

6.17

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