P2 Unit 6 Mains electricity lesson 1

Lesson 1 AC and cables/plugs

Aim: Use oscilloscope traces to compare direct and alternating potential differences.

10 min Starter: Introduction to AC and DC electricity/oscilloscopes.

20 min Main 1: Key points and text book questions.

Copy down key points about AC electricity and solve some oscilloscope problems plus text book questions on pg 249.

· Cell and batteries supply current that passes in one direction (direct current)
· An alternating current constantly changes direction. Mains electricity is an AC supply. In the UK it has a frequency of 50 cycles per second (50 Hz)
· UK mains supply is about 230 Volts.
· The live terminal of the mains supply alternates between positive and negative potential with respect to the neutral terminal (Higher tier)
· The neutral terminal stays at a potential close to zero with respect to the earth (Higher tier)

20 min Main 2: Cables and plugs

Draw a diagram of the correct structure for a cable and a plug using pg 250 to help. Text book questions on pg 251 for early finishers.

The image and text are from BBC Bytesize which is a very useful revision tool. The link to material covered in todays lesson can be found here. http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/mainselectrev1.shtml

10 min Plenary: Exam style question
On plugs from the foundation paper January 2007

P2 Unit 5 5.2 Resistance & 5.3 current potential difference graphs

Additional Science P2 Unit 5: Current electricity.

Lesson 2: Resistance & current-potential difference graphs

Textbook section P2 5.2 & 5.3

Aim: How do wires, filament lamps, diodes, LDR’s & thermistors affect the resistance in an electrical circuit?

Starter (10 min):
Students recap last lesson by answering summary questions 1 & 2 on pg 237 of the textbook. Mr C will provide the answers and students should self assess their work.

Main Activity 1 (20 min): Current/Potential difference graphs for wires, filament lamps and diodes.

Students are given some data and have to draw a current/potential difference graph for the above components. Mr C will provide the data but students can use their own data for wires and filament lamps if they completed the experiment from last lesson. Students should note the shape of the graphs.

Provided the temperature is kept constant the resistance of a wire is always the same. Because R = V/I the resistance (slope of the graph) is always a straight line through the origin of the graph.
The current-potential difference graph for a filament lamp curves. So the current is not directly proportional to the potential difference. Resistance in a filament lamp increases as the filament lamp heats up, so resistance increases when current increases. Reversing the direction of the current makes no difference to the shape of the graph.
The current through a diode flows in one direction only. In the reverse direction the diode has a very high resistance so the current is virtually zero.

Main Activity 2 (20 min): Thermistors and LDR’s

Mr C will describe how Thermistors and Light dependent resistors affect electrical circuits using Virtual Physics Laboratory.
Students then have to match the five components discussed today to descriptions of their effects on electrical circuits.

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/resistancerev3.shtml more information from BBC Bytesize.

Plenary (5 min): Four key questions

From Physics revision cards.

AQA Specification: Unit Physics 2.13.6

P2 2.5 Falling objects

Lesson 4: Falling objects

Textbook section P2 2.5

Aim: How does a parachute work?

Starter (10 min): F=ma becomes weight (N) = mass (kg) x acceleration due to gravity (m/s2)
When objects fall freely, the resultant force acting on them is the Earth’s force provided by Earth’s gravitational field. This will make an object accelerate at about 10 ms2 close to the Earth’s surface.

We call the force of gravity ‘weight’ and the acceleration ‘the acceleration due to gravity’.

F=ma becomes weight = mass x gravitational field strength.

When objects fall through fluids (such as water and air), the fluid exerts frictional forces on the object. > the velocity of the object then > frictional force. Eventually the two forces (weight & friction) will balance, resultant force = zero and the object moves at a steady velocity. This is called the ‘terminal velocity’. Possibly show the ball bearing in air, water, and honey demonstration.

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/forcemassrev4.shtml see BBC Bytesize for more on this topic.

Main activity (30 min): Egg parachute competition.

Students have to think about what makes a good parachute (one that creates the most drag force/air resistance so > deceleration, <> time taken to hit the ground). They have 15 min to build an egg parachute which will then be tested outside (materials plastic bags, string, tape, 1 egg per team).
Rules
1. No cushioning for the egg
2. If the egg breaks you are disqualified
3. The team whose parachute took the longest to hit the ground without the egg breaking are the winners. The winning team will receive a prize.

Plenary (15 min):

Students are given a velocity time graph for a falling object, they have to describe what is happening at each stage using the key words and terms. They should also calculate the size of the forces using the equation w = m x g.
Accelerates, Weight, Gravity, Drag force, Increase, Decrease, Terminal velocity, greater than, equal to

AQA Specification – Physics 2.13.2
· The faster a body moves through a fluid the greater the frictional force that acts on it.
· A body falling through a fluid will initially accelerate due to the force of gravity. Eventually the resultant force on the body will be zero and it will fall at its terminal velocity.
· Calculate the weight of a body using: weight (newton, N) = mass (kilogram, kg) x gravitational field strength (newton/kilogram, N/kg)Draw and interpret velocity-time graphs for bodies that reach terminal velocity, including a consideration of the forces acting on the body.

P2 Unit 2.4 On the road

Lesson 3: On the road

Textbook section P2 2.4

Aim: What factors affect the stopping distance of vehicle on the road?

Starter 10 min: 10 key questions that provide a recap of the previous two lessons. These should be attempted without books. Mr C will provide the answers and students should self assess their work.

Main activity 30 min:
When a vehicle is travelling at a steady speed the resultant force acting on it is zero, so driving forces are equal & opposite to frictional forces.
The braking force needed to stop that vehicle depends on the velocity and mass of the vehicle. > velocity and/or > mass = > braking force.
The total stopping distance of a vehicle is the distance it travels during the driver’s reaction time (the thinking distance) plus the distance it travels under the braking force (the braking distance).
Stopping distance = thinking distance + braking distance. With the same driver and car the thinking & braking distance will increase when the initial velocity increases.
The thinking distance will increase if the driver is tired or under the influence.
The braking distance can be increased by poorly maintained roads, bad weather conditions & the condition of the car i.e. worn brakes or tyres.

Students have to...
1. Use the textbook to draw a diagram or series of diagrams that summarise the above, it should be simple and concise and include as many key points as possible. To help them begin a diagram of Mr Average in his average car is shown on the board.
What is a stopping distance? Explained by Mr Average.
What factors affect braking force?
What factors affect the thinking distance and braking distance?
2. Complete summary questions 1 & 2 on pg 203 of the text book. Mr C will provide answers at the end of the lesson.
3. If there is time the lesson can be finished with some reaction tests using software on the computer.

http://www.gcse.com/fm/stopping_distances.htm a good summary of the material covered in this lesson.

Plenary (10 min)...
Students can try some practice exam questions. Mr C will give the answers and students should mark and correct their own work.

AQA Specification – Physics 2.13.2
· When a vehicle travels at a steady speed the frictional forces balance the driving forces.
· The greater the speed of a vehicle the greater the braking force needed to stop it in a certain distance.
· The stopping distance of a vehicle depends on the distance the vehicle travels during the drivers reaction time and the distance it travels under the braking force.
· A driver’s reaction time can be affected by tiredness, drugs and alcohol.
· A vehicle’s braking distance can be affected by adverse road and weather conditions and poor condition of the vehicle.

P2 Unit 5 lesson 1 Resistance & p.d/current graphs

Resistance & current/voltage graphsLesson P2 5.1/2/3

Aim: Calculate resistance (ohms) and draw current/p.d graphs for a wire, filament lamp and a diode.
Key words: Potential difference, resistance, voltage (p.d), current, filament lamp, diode.

Starter: Recap of circuits and introduction to Resistance equation...
Resistance (ohms) = Potential difference (Volts)/current (amperes).
R = V/I. Students try some examples to practice using the equation.

Main: Mr C will introduce current/p.d graphs and quickly demonstrate the circuit that you will need to set up. You will be changing the voltage in the circuit and measuring the effect this has on the current using an ammeter. You will then need to record your results in a table and plot them on a graph. The slope of the line represents the resistance in the circuit. Make sure you investigate the effect that wires, filament lamps and diodes have on resistance.
Write a short conclusion that summarises your observations. How do the various appliances effect resistance in electrical circuits (the slope of the graph).

Plenary: Mr C will go over what you should have observed during the experiment. Make sure you assess your own work so you know your understanding is correct.
To end the lesson Mr C will explain how thermistor’s and LDR’s (Light dependent resistors) affect resistance in a circuit. If there is time the summary questions on pg 239 of the textbook can be attempted.

Homework: from H/W book.

AQA Specification Link up
Physics 2.13.6

Unit P2 Lesson 3.2 Kinetic energy

Lesson P2 3.2 Kinetic energy

Aim: What energy transformations happen when a catapult is drawn back and then fired?

Key words: Kinetic energy, Elastic potential energy.

Starter:
To provide a recap about what you learnt last lesson Mr C will provide some work done = force x distance problems for you to solve.

Main:
Your job is to use the textbooks and find out what Kinetic energy and elastic potential energy are and use what you have found out to answer Question 1 in the summary questions (see the aim of the lesson). If possible I would like you to answer this question in the form of a comic strip – in each frame you should show what actions take place (for example a person pulls back the catapult) and what energy transformations take place (chemical energy in the body is transformed into kinetic energy then elastic potential energy & some heat energy in the catapult). You can also attempt question 2 (a) and (b). Mr C will go over the answers and any problems that arise.

Plenary:
You will try some exam style questions about what has been covered in the previous two lessons. Remember practice makes perfect!

Which of the objects are storing elastic potential energy?

Explain the reason for your choice or choices. (3 marks).

Homework: None set.

AQA Specification link up – unit Physics 2.13.5
· For an object that is able to recover its original shape elastic potential energy is the energy stored in an object when work is done on the object to change its shape.
· The kinetic energy of a body depends on its mass and speed.
· Discuss the transformation of kinetic energy to other forms of energy in particular situations.

P2 Unit 3 Lesson 1

Energy and work Lesson P2 3.1

Aim: Find out what work is and use the equation work done (J) = force (N) x distance (m)

Key words: work, joules, force, Newton, distance.

Starter: Some of the class are offered a fudge bar to eat. However having eaten the fudge bar they then have to use up the energy consumed by climbing some stairs outside the lab. We can work out how many times they have to climb the stairs using the equation work done = force x distance.
You will then need to take some notes about what has been discussed.

Main: Students attempt some practice examples of using the equation and then attempt the summary questions on pg 211 of the text book.

Plenary: Answers to the summary questions and examples are given, you should self assess your work. A brief class discussion will then take place to iron out any problems or misconceptions that may have arisen during the lesson.
Finally there will be a reminder about what happens to energy when work takes place using the example of a man riding a bike.

Homework: None set.

AQA Specification Link up Unit: Physics 2.13.3
· When a force causes a body to move through a distance, energy is transferred and work is done.
· Work done = energy transferred.
· The amount of work done, force and distance are related by the equation: work done = force applied x distance moved in the direction of force. Work done against frictional force is mainly transformed into heat.

P2 Unit 4 Lesson 2 Charge on the move

Charge on the move Lesson P2 4.2

Aim: Explain, in terms of the flow of electrons, how and when a metallic ring can be charged.

Key words: Electron, Proton, Flow of charge, Conductor, Earth.

Starter: Students to draw energy transfer diagrams for a torch. This provides a recap of material & knowledge covered in Year 9.

Main: Demonstration and explanations of the flow of charge using a gold leaf electroscope, charged rings and simple circuit model (virtual physics lab).

Students should make some notes explaining that current is the flow of electrical charge.
Students to draw a simple cartoon strip explaining what they observed during the ‘ring charging demonstration’. Particular attention should be given to the movement of electrons. Remember protons do not move, they are trapped in the nucleus of their respective atoms!

H Extension: Explaining lightning. H students should understand that as we supply a conductor with more and more charge, it’s electric potential energy increases. The potential difference between the conductor and the ground also increases. If the p.d becomes high enough then a spark may ‘jump’ between the charged object and a nearby earthed object. This is what happens when lightning strikes clock towers (see back to the future!) etc.

Plenary: Summary questions on Page 227 of the additional Science textbook. AfL self assessment of answers to questions.

Homework: Page 37 of H/W book & Q 16 on page 36.

AQA Specification Link up
· Electrical charges can move easily through some substances, e.g. metals.
· The rate of flow of electrical charge is called the current.
· A charged body can be discharged by connecting it to earth with a conductor, charge then flows through the conductor.
· Greater charge = greater p.d between a body & earth. If the p.d becomes high enough, a spark may jump across the gap between the body and any earthed conductor that is bought near it (HT only).