Preface and acknowledgements.

There are 62 experiments in this volume, covering practical work on electricity and heat. They are arranged as teacher’s notes followed by the student’s worksheet. The students and teachers notes can be photocopied for use within the purchasing institution. The accompanying CD includes setup files referred to in the student’s notes and will be automatically installed into the EASYSENSE software. The installed software creates an onscreen worksheet, use the Open worksheet route from the EASYSENSE Homepage. The student will see the student’s worksheet, slightly reworded from the printed notes, and an option to launch. Launching will use a setup file to configure the logger and software and open EASYSENSE. The student can, at any time, swap between the experiment and worksheet. This facility needs Acrobat reader to be installed. It is hoped the experiments will make it easier for teachers to introduce data logging to students in a meaningful manner. The experiments cover a wide range of ability levels and curriculum requirements. They have been organised into topic areas, where possible. Within each topic area, higher numbered experiments indicate a more complex or challenging experiment. Experiments with a following a, b or c are variations of the same experiment using different apparatus. These experiments have been written after use in a classroom, and they have come from many sources. It is not the intention to suggest that they are original, they are experiments that users have asked for, or have told us are useful for the teaching of science and introducing students to data logging. The teachers conducting the experiments should carry out a correct assessment of the safety risks associated with the experiment. The inclusion or exclusion of safety information is not an indication of responsibility by the publisher. Teachers must follow local safety regulations and advice to ensure the safety of the teacher and students is maintained. Disposal and use of chemicals associated with the experiments should follow local regulations.

The help and ideas of the following are gratefully acknowledged. Dr Roy Barton of the University of East Anglia.

Ian Birell of SSERC. Iain Davison ex Head of Physics St. Cuthbert Mayne School,Devon and Data Harvest.

Barry Hawkins of Data Harvest. Barbara Higginbotham of Data Harvest.

Paul Horton ex Head of Science, Cornwallis school, Kent. David Keenahan, Gonzaga College S.J, Dublin

Document number DO197 issue 2

Electricity and heat Contents i

Student’s instructions

01 The coffee problem, “Must phone off, the coffee is getting cold” .................................01 -.1

02 Cooling by evaporation .................................................................................................02 -.1

03 How does sweating keep you cool? A practical application of cooling by evaporation.03 - 1

04 Cooling substances .......................................................................................................04 - 1

05 Heat transfer ..................................................................................................................05 - 1

06 How does the surface of an object affect its ability to radiate energy (Leslie’s cube)...06 - 1

07 Relationship between temperature and radiated energy ..............................................07 - 1

08 What type of surface absorbs radiant energy? .............................................................08 - 1

09 Why insulate houses? A hotter house for less greenhouse gas ...................................09 - 1

10 Conduction and convection in gases.............................................................................10 - 1

11 Conduction and convection in liquids ............................................................................11 - 1

12 Conduction and convection in solids .............................................................................12 - 1

13 Which is the best conductor of heat .............................................................................13 - 1

14 Which material is the best absorber of heat? ............................................................... 14 – 1

15 Residual heat: Thermal imaging....................................................................................15 - 1

16 Residual heat: Finding where a natural disaster survivor is buried...............................16 - 1

17 Hot stuff! ........................................................................................................................17 - 1

18 Verification of the equivalence of heat energy liberated to electrical energy

dissipated............................................................................................................................18 - 1

19 Stefan – Boltzmann law using a tungsten filament lamp...............................................19 - 1

20 Calibration of a thermometer .........................................................................................20 - 1

21 Specific heat capacity for a liquid. Experiment to measure the specific heat capacity of water ...................................................................................................................................21 - 1

22 Specific heat capacity of a solid. Experiment to measure the specific heat cpacity of a metal block..........................................................................................................................22 - 1

24a Angle of the sun and collected energy – using sunlight ............................................24a - 1

24b Angle of the sun and collected energy – using an artificial sun ................................24b - 1

25a What changes the current in a circuit (meters)..........................................................25a - 1

25b What changes current in circuit (snapshot) ...............................................................25b - 1

26 Good and bad connectors .............................................................................................26 - 1

27 Connecting resistors together........................................................................................27 - 1

28 What happens to the brightness of a bulb when the voltage is changed......................28 - 1

29 Can you use the bulb brightness to measure current ...................................................29 - 1

30a Current and voltage (against time) ............................................................................30a - 1

30b Current and voltage (as an x –y graph).....................................................................30b - 1

31 Electric current in circuits – series circuits – current has no choice ..............................31 - 1

32 Electric current in circuits – Parallel circuits – current has a choice..............................32 - 1

33 Electric current in circuits – current and voltage in a simple series circuit ...................33 - 1

34 Ohm’s Law.....................................................................................................................34 - 1

Electricity and heat Contents ii

34a Ohm’s Law (voltage and current) ............................................................................. 34a – 1

35 Electrical characteristics ................................................................................................35 - 1

35a Electrical characteristics of a resistor and lamp ........................................................35a - 1

35b Electrical characteristics of a Diode and an LED ......................................................35b - 1

36 Time constant for a capacitor – resistor circuit..............................................................36 - 1

37 Charge stored on a capacitor ........................................................................................37 - 1

38 Energy stored in a capacitor..........................................................................................38 - 1

39 Startup current of a light bulb ........................................................................................39 - 1

40 Long wires, less power? ................................................................................................40 - 1

41 Induction of a current in a conductor .............................................................................41 - 1

42 Induction of a voltage in a coil .......................................................................................42 - 1

43 What happens when a magnet spins in a coil? .............................................................43 - 1

44 Efficiency of an electric motor / generator .....................................................................44 - 1

44a Efficiency of an electric generator ...............................................................................45 - 1

44b Efficiency of an electric motor....................................................................................44b - 1

45 Electricity from water power ..........................................................................................45 - 1

46 Change in the magnetic field strength between magnets .............................................46 - 1

47 Measuring the strength of an electromagnet.................................................................47 - 1

48 Strength of an electromagnet. Measuring volts and current .........................................48 - 1

49 What happens if an alternating current is used to make an electromagnet ..................49 - 1

50 How does the magnetic field strength due to a coil vary as the current varies .............50 - 1

51 Investigating the force acting on a current carrying conductor in a magnetic field .......51 - 1

52 The variation of the magnetic field strength along the axis of a coil..............................52 - 1

53 Mapping the magnetic field of a bar magnet .................................................................53 - 1

54 Efficiency of a transformer.............................................................................................54 - 1

55 The d.c. characteristics of a diode.................................................................................55 - 1

56a Diodes: A.C. rectification ..........................................................................................56a - 1

56b Diodes: A.C. Bridge rectification ...............................................................................56b - 1

57 The input characteristic of a transistor .........................................................................57 - 1

58 Transistor as a switch and a current amplifier ..............................................................58 - 1

59 Reactance and phase in a capacitor ............................................................................59 - 1

60 C –R circuit. How does the impedance and phase difference change as the frequency increases ...........................................................................................................................60 - 1

61 L – R circuit. How does the impedance change as the frequency increases ................61 -1

62 Resonance in a series LCR circuit ................................................................................62 -1

Electricity and heat Contents iii

Teachers notes

T01 The coffee problem, “Must phone off, the coffee is getting cold” .............................T01 - 1

T02 Cooling by evaporation .............................................................................................T02 - 1

T03 How does sweating keep you cool? A practical application of cooling by

evaporation ......................................................................................................................T03 - 1

T04 Cooling substances ...................................................................................................T04 - 1

T05 Heat transfer..............................................................................................................T05 - 1

T06 How does the surface of an object affect its ability to radiate energy

(Leslie’s cube)...................................................................................................................T06 - 1

T08 What type of surface absorbs radiant energy? ........................................................T08 - 1

T07 Relationship between temperature and radiated energy ..........................................T07 - 1

T09 Why insulate houses? A hotter house for less greenhouse gas ...............................T09 - 1

T10 Conduction and convection in gases ........................................................................T10 - 1

T11 Conduction and convection in liquids........................................................................T11 - 1

T12 Conduction and convection in solids........................................................................T12 – 1

T13 Which is the best conductor of heat? .......................................................................T13 - 1

T14 Which material is the best absorber of heat?............................................................T14 - 1

T15 Residual heat: Thermal imaging ...............................................................................T15 - 1

T16 Residual heat: Finding where a natural disaster survivor is buried...........................T16 - 1

T17 Hot stuff! ....................................................................................................................T17 - 1

T18 Verification of the equivalence of heat energy liberated to electrical energy

dissipated..........................................................................................................................T18 - 1

T19 Stefan – Boltzmann law using a tungsten filament lamp ..........................................T19 - 1

T20 Calibration of a thermometer.....................................................................................T20 - 1

T21 Specific heat capacity for a liquid. Experiment to measure the specific heat capacity of water .................................................................................................................................T21 - 1

T22 Specific heat capacity of a solid. Experiment to measure the specific heat capacity of a metal block........................................................................................................................T22 - 1

T24a/b Angle of the sun and collected energy – a) using sunlight

b)using an artificial sun................................................................................................T24a/b - 1

T24b Angle of the sun and collected energy – using an artificial sun ............................T24b - 1

T25a What changes the current in a circuit (meters) .....................................................T25a - 1

T25b What changes current in circuit (snapshot)...........................................................T25b - 1

T26 Good and bad connectors .........................................................................................T26 - 1

T27 Connecting resistors together ...................................................................................T27 - 1

T28 What happens to the brightness of a bulb when the voltage is changed..................T28 - 1

T29 Can you use the bulb brightness to measure current ..............................................T29 – 1

T30a/b Current and voltage a) against time) b) as an x –y graph).............................T30 a/b - 1

T31 Electric current in circuits – series circuits – current has no choice..........................T31 - 1

T32 Electric current in circuits – Parallel circuits – current has a choice .........................T32 - 1

Electricity and heat Contents iv

T33 Electric current in circuits – current and voltage in a simple series circuit ...............T33 - 1

T34 Ohm’s Law.................................................................................................................T34 - 1

T35a/b Electrical characteristics resistor, lamp diode and LED................................T35 a/b - 1

T36 Time constant for a capacitor – resistor circuit..........................................................T36 - 1

T37 Charge stored on a capacitor ....................................................................................T37 - 1

T38 Energy stored in a capacitor......................................................................................T38 - 1

T39 Startup current of a light bulb ....................................................................................T39 - 1

T40 Long wires, less power?............................................................................................T40 - 1

T41 Induction of a current in a conductor.........................................................................T41 - 1

T42 Induction of a voltage in a coil ...................................................................................T42 - 1

T43 What happens when a magnet spins in a coil?.........................................................T43 - 1

T44 Efficiency of an electric motor / generator.................................................................T44 - 1

T45 Electricity from water power ......................................................................................T45 - 1

T46 Change in the magnetic field strength between magnets .........................................T46 - 1

T47 Measuring the strength of an electromagnet.............................................................T47 - 1

T48 Strength of an electromagnet. Measuring volts and current .....................................T48 - 1

T49 What happens if an alternating current is used to make an electromagnet..............T49 - 1

T50 How does the magnetic field strength due to a coil vary as the current varies.........T50 - 1

T51 Investigating the force acting on a current carrying conductor in a magnetic field ...T51 - 1

T52 The variation of the magnetic field strength along the axis of a coil .........................T52 - 1

T53 Mapping the magnetic field of a bar magnet .............................................................T53 - 1

T54 Efficiency of a transformer.........................................................................................T54 - 1

T55 The d.c. characteristics of a diode ............................................................................T55 - 1

T56 Diodes: A.C. rectification ..........................................................................................T56 - 1

T57 The input characteristic of a transistor .....................................................................T57 - 1

T58 Transistor as a switch and a current amplifier ..........................................................T58 - 1

T59 Reactance and phase in a capacitor ........................................................................T59 - 1

T60 C –R circuit. How does the impedance and phase difference change as the frequency increases .........................................................................................................................T60 - 1

T61 L – R circuit. How does the impedance change as the frequency increases ..........T61 - 1

T62 Resonance in a series LCR circuit ...........................................................................T62 - 1

Electricity and heat Contents v

Student’s instructions Sensors used Page

01 The coffee problem, “Must phone off, the coffee is getting cold”

Temperature 01 - 1

02 Cooling by evaporation Temperature 02 - 1

03 How does sweating keep you cool? A practical application of cooling by evaporation

Temperature 03 - 1

04 Cooling substances Temperature 04 - 1

05 Heat transfer Temperature 05 - 1

06 How does the surface of an object affect its ability to radiate energy (Leslie’s cube)

Infrared,Temperature 06 - 1

07 Relationship between temperature and radiated energy

Infrared,Temperature 07 - 1

08 What type of surface absorbs radiant energy? Infrared,Temperature 08 - 1

09 Why insulate houses? A hotter house for less greenhouse gas

Temperature 09 - 1

10 Conduction and convection in gases Temperature 10 - 1

11 Conduction and convection in liquids Temperature 11 - 1

12 Conduction and convection in solids Temperature 12 - 1

13 Which is the best conductor of heat? Temperature 13 - 1

14 Which material is the best absorber of heat? Temperature 14 - 1

15 Residual heat: Thermal imaging Infrared 15 - 1

16 Residual heat: Finding where a natural disaster survivor is buried

Infrared 16 - 1

17 Hot stuff! Infrared 17 - 1

18 Verification of the equivalence of heat energy liberated to electrical energy dissipated

Voltage, Current, Temperature

18 - 1

19 Stefan – Boltzmann law using a tungsten filament lamp

Infrared, Voltage, Current 19 - 1

20 Calibration of a thermometer Temperature, Current 20 - 1

21 Specific heat capacity for a liquid. Experiment to measure the specific heat capacity of water

Voltage, Current, Temperature

21 - 1

22 Specific heat capacity of a solid. Experiment to measure the specific heat cpacity of a metal block

Voltage, Current, Temperature

22 - 1

24a Angle of the sun and collected energy – using sunlight

Heat Flow, Temperature 24a - 1

24b Angle of the sun and collected energy – using an artificial sun

Heat Flow, Temperature 24b - 1

25a What changes the current in a circuit (meters) Current 25a - 1

25b What changes current in circuit (snapshot) Current 25b - 1

26 Good and bad connectors Current 26 - 1

Electricity and heat Contents vi

27 Connecting resistors together Voltage, Current 27 - 1

28 What happens to the brightness of a bulb when the voltage is changed

Light 28 - 1

29 Can you use the bulb brightness to measure current

Current, Light 29 - 1

30a Current and voltage (against time) Current, Voltage 30a - 1

30b Current and voltage (as an x –y graph) Current, Voltage 30b - 1

31 Electric current in circuits – series circuits – current has no choice

Current 31 - 1

32 Electric current in circuits – Parallel circuits – current has a choice

Current 32 - 1

33 Electric current in circuits – current and voltage in a simple series circuit

Current, Voltage 33 – 1

34 Ohm’s Law Current, Voltage 34 – 1

34a Ohm’s Law Current, Voltage 34a – 1

35 Electrical characteristics Current, Voltage 35 - 1

35a Electrical characteristics of a resistor and lamp Current, Voltage 35a - 1

35b Electrical characteristics of a Diode and an LED Current, Voltage 35b - 1

36 Time constant for a capacitor – resistor circuit Current, Voltage 36 - 1

37 Charge stored on a capacitor Current, Voltage 37 - 1

38 Energy stored in a capacitor Current, Voltage 38 - 1

39 Startup current of a light bulb Current, Voltage, Light (fast)

39 - 1

40 Long wires, less power? Light, Current, Voltage 40 -1

41 Induction of a current in a conductor Current 41 - 1

42 Induction of a voltage in a coil Voltage 42 - 1

43 What happens when a magnet spins in a coil? Voltage 43 - 1

44 Efficiency of an electric motor / generator Current, Voltage 44 - 1

44a Efficiency of an electric generator Current, Voltage 45 - 1

44b Efficiency of an electric motor Current, Voltage 44b - 1

45 Electricity from water power Current, Voltage 45 - 1

46 Change in the magnetic field strength between magnets

Magnetic field 46 - 1

47 Measuring the strength of an electromagnet Magnetic field 47 - 1

48 Strength of an electromagnet. Measuring volts and current

Magnetic field, Voltage, Current

48 - 1

49 What happens if an alternating current is used to make an electromagnet

Magnetic field, Voltage, Current

49 – 1

50 How does the magnetic field strength due to a coil vary as the current varies

Magnetic field, Current 50 - 1

51 Investigating the force acting on a current carrying conductor in a magnetic field

Current 51 - 1

Electricity and heat Contents vii

52 The variation of the magnetic field strength along the axis of a coil

Magnetic field, Current 52 - 1

53 Mapping the magnetic field of a bar magnet Magnetic field 53 - 1

54 Efficiency of a transformer Voltage, Current 54 - 1

55 The d.c. characteristics of a diode Voltage, Current 55 - 1

56a Diodes: A.C. rectification Voltage 56a - 1

56b Diodes: A.C. Bridge rectification Voltage 56b - 1

57 The input characteristic of a transistor Voltage, Current 57 - 1

58 Transistor as a switch and a current amplifier Voltage, Current 58 - 1

59 Reactance and phase in a capacitor Voltage, Current 59 - 1

60 C –R circuit. How does the impedance and phase difference change as the frequency increases

Voltage, Current 60 - 1

61 L – R circuit. How does the impedance change as the frequency increases

Voltage, Current 61 -1

62 Resonance in a series LCR circuit Voltage, Current 62 -1

Electricity and heat Contents viii

Sensors: Temperature Loggers: Any EASYSENSE

Logging time: 15 minutes

Electricity and Heat T01 - 1

Physics

Electricity and Heat

Teacher’s notes

01 The coffee problem

“Must phone off, the coffee is getting cold”

Read. This is a classic problem. A simple search on the internet will reveal countless variations of the same experiment and as many explanations many of them requiring a good understanding of quantum physics!

In its simplest for the problem is “if I start with two liquids, one hot and one cold (cooler) and I mix them together, will the time taken for cooling be any different from adding the liquids together after the hot one had been allowed to cool a bit”.

An alternative is the often quoted statement “hot water placed into a freezer will produce ice cubes quicker than cold water”

Every ounce of logic tells us it should make no difference. Practical experience leads us to perceive there is a difference. The investigation therefore attempts to measure the “problem” scientifically.

The variation used in this experiment is;

"I have just made a cup of coffee when the telephone rings. Should I put milk in before answering, or wait until the call is over? I want the coffee to be as warm as possible when I have finished the call."

This is a problem about the cooling of a mixture of hot and cold liquids.

In the experiment students will monitor the temperature of two beakers which each contain equal volumes of hot “coffee” (hot water) of the same temperature. In one beaker cold water will be added near the start (while the “coffee” is still very hot)and in the other the cold water will be added after five minutes (after the “coffee has been allowed to cool for a while). The cold water needs to be controlled as well, its temperature can alter as it is waiting to be used, it is unlikely that this has been done in the “casual” investigation.

Ask for predictions as to which cup will be at the highest temperature when the time for the experiment is finished.

One of the things that has been noticed when preparing the notes for this experiment is that great care is made in making the hot liquids the same temperature at the start but little effort is made in keeping the cold liquids controlled, cold things do warm up when left in the room!

Apparatus. 1. An EASYSENSE logger 2. 2 Smart Q Temperature sensors 3. 2 beakers of the same size (to hold at least 200 cm

3)

4. 2 measuring cylinders 5. Hot water 6. Cold water

Setup of software and logger. Use the setup 01 Coffee problem If you wish to set up the logger manually, use the details in the table below.

Recording method Total recording time

Graph 20 minutes

Notes. The experiment uses simple water as the “coffee” for some students the idea of modeling is difficult; they have not developed the cognitive skills to transfer the information from one scenario to another. With this in mind, it would be worth the effort to give a repeat of the experiment using coffee and milk.

There may be slight difference between sensors, it is suggested that both sensors are placed in water of the same temperature for a few minutes to identify the difference (if any). This can then be taken into account when temperatures from the sensors are being compared.

Make sure the cooling drinks are in the same conditions, the differences are slight and any external input of energy or increase in energy loss will have a significant effect. Control direct sunlight, hot air from heating systems, air movements etc.

Placing the “coffee cups” on an insulating mat will prevent unequal heat loss from the cup to the “table”

Students should be encouraged to express their own ideas and predictions. It is a good investigation for creating discussion and this part of the work should not be neglected.

Electricity and Heat T01 - 2

Sensors: Temperature Loggers: Any EASYSENSE

Logging time: 15 minutes

Electricity and Heat 01 - 1

Physics

Electricity and Heat

01 The coffee problem

“Must phone off, the coffee is getting cold”

Read. "I have just made a cup of coffee when the telephone rings. Should I put milk in before answering, or wait until the call is over? I want the coffee to be as warm as possible when I have finished the call."

This is a problem about the cooling of a mixture of hot and cold liquids.

In the experiment, you will monitor the temperature of two beakers which each contain equal volumes of hot “coffee” (hot water) of the same temperature. In one beaker cold water will be added near the start (while the “coffee” is still very hot)and in the other the cold water will be added after five minutes (after the “coffee has been allowed to cool for a while)

Try to predict which will be at the highest temperature when the time for the experiment is finished.

What you need. 1. An EASYSENSE logger 2. 2 Smart Q Temperature sensors 3. 2 beakers of the same size (to hold at least 200 cm

3)

4. 2 measuring cylinders 5. Hot water 6. Cold water

What to do. 1. Assemble the apparatus as shown in the diagram. Clamp the temperature probes so they do not

touch the sides of the cup and add approximately 100 cm3 of hot water.

2. Start EASYSENSE and select Open setup from the Home page. Open the setup file Data Harvest Investigations \ Setup files \ Physics L3 Electricity + Heat \ 01 Coffee problem.

3. Click Start to begin logging

4. After 1 minute add 50 cm3 of cold water to one of the cups. Do not stir.

5. After five minutes add 50 cm3 of cold water to the other cup. Do not stir.

Results. Identify and label the set of data that corresponds to each of the beakers/temperature probes.

The results can be saved, printed or copied into your report document as required.

Questions. 1. What situation results in the water being warmest after ten minutes? Explain the result

2. What advice would you give to a person making the coffee as the telephone rings?

More to do. 1. Try the experiment with real coffee. Do you get the same results?

2. Does it matter if the milk is in the cup before or after you fill the cup with the hot drink? (Is this the same problem?)

3. Does the shape of the cup have an effect?

4. Do the cups you get from “take-aways” keep the drink hotter for any longer?

5. Does the cap on a “take out” coffee keep the drink hot?

6. What happens if the room is hot or cold?

7. What about cold drinks getting hotter?

Electricity and Heat 01 - 2