Concept 2

1. Concept 2 Energy Transfer

2. Concept 2 Vocabulary Terms Static electricity Proton Electron Neutral Charge separation Electrical discharge Electrical current Circuit Amperes (A) Conductors Load Voltage Potential difference Volt (V) Voltmeter Short circuit Insulators Fuses Circuit breakers

3. Concept 2 Vocabulary Terms Electrochemical cell Dry cell Electrolyte Ion Electrode Wet cell Primary cell Rechargeable cell Secondary cell Battery Electrolysis Electrochemistry Electroplating

4. Concept 2 – Vocabulary Terms • Conductor • Insulator • Resistor • Resistance • Ohms (Ω) • Variable resistor • Rheostat • Ohm’s Law • Ammeter • Schematic • Schematic diagram • Series circuit • Parallel circuit • Transistor • Microcircuit

5. Concept 2 – Energy Transfer Learning Concept • Investigate and evaluate the use of different electrodes, electrolytes and electrolytic concentrations in designing electrical storage cells

6. Concept 2 – Energy Transfer • Recall: • Chemical energy is transformed into electrical energy in battery-powered devices • An electrochemical cell is a device which has different metals in a solution containing a salt or acid

7. Concept 2 – Energy Transfer • In an electrochemical cell, there are two metal electrodes surrounded by an electrolyte, a substance that can conduct electricity

8. Concept 2 – Energy Transfer Learning Concept • Assess the potential danger of electrical devices, by referring to the voltage and current rating (amperage) of the devices • Distinguish between safe and unsafe activities

9. Concept 2 – Energy Transfer • Two aspects of electricity must be considered when looking electrical dangers • Voltage • The measure of how much energy is carried by each particle • Ampere • The rate at which an electrical current flows http://i881.photobucket.com

10. Concept 2 – Energy Transfer • High voltage is more dangerous than low voltage • Small voltages can kill if the shock carries a significant amount of amps • The number of amps is more important than voltage when assessing potential danger http://wpcontent.answcdn.com http://static.newworldencyclopedia.org

11. Concept 2 – Energy Transfer • 50,000 V is more likely to kill than 10 V • 0.001 A passed through your body won’t likely be felt • Current in the range of 0.015 A to 0.02 A causes a painful shock and loss of muscle control • Currents as low as 0.1 A can be fatal Electric eel can discharge 600 V at 1.0 A www.aqua.org

12. Concept 2 – Energy Transfer • Taser(stun) guns can carry up to 50,000 volts • Can deliver up to 1,500 V to a person’s body • Small current of 0.002 to 0.03 amps http://thebsreport.files.wordpress.com http://www.cbc.ca/news/canada/story/2009/03/18/f-taser-faq.html

13. Concept 2 – Energy Transfer • Electrical outlets in Canada deliver 120 volts of electricity • A light bulb draws about 0.5A while a toaster pulls 5A • Possible to suffer fatal shock from a household outlet http://www.cbc.ca/news/canada/story/2009/03/18/f-taser-faq.html

14. Concept 2 – Energy Transfer Science Log • Make a list of 5 safety pointers for use with electrical devices (reference pg 285) • ex. Do not use electrical devices when near or in water unless they are specially designed www.auctionpax.co.uk

15. Concept 2 – Energy Transfer • Learning Concept • Distinguish between static and current electricity • Identify example evidence of each

16. Concept 2 – Energy Transfer • Recall: • The proton has a positive charge • The electron has a negative charge • Most objects have equal amounts of positive and negative charges, which makes them neutral

17. Concept 2 – Energy Transfer Charge separation occurs when charged objects are brought close to neutral objects http://4.bp.blogspot.com

18. Concept 2 – Energy Transfer • Rubbing the balloon on your hair transfers electrons (e-) from your hair to the balloon • Bringing the charged balloon to the wall repels the e- in the wall but attracts the protons

19. Concept 2 – Energy Transfer • The Laws of Electrical Charges • Opposite charges attract each other • Like charges repel each other http://learn.uci.ed

20. Concept 2 – Electrical Energy • Electrical discharge is observed as a spark • Static energy does not flow in a current but can build up and discharge • Electrons build up in your body • Doorknob becomes positively charged as “your” electrons repel the doorknob electrons • “Your” electrons are attracted to the doorknob’s protons www.school-for-champions.com

21. Concept 2 – Energy Transfer • Van de Graaff generator • http://www.youtube.com/watch?v=7qgM1A3pgkQ&feature=related http://1.bp.blogspot.com http://4.bp.blogspot.com

22. Concept 2 – Energy Transfer • While static energy builds up and discharges, it does not flow continuously • Electrical currents are steady flows of charged particles • This is the type of energy used to operate electrical devices http://upload.wikimedia.org

23. Concept 2 – Energy Transfer Learning Concept • Identify electrical conductors and insulators • Compare resistance of different materials to electric flow

24. Concept 2 – Energy Transfer • Insulators do not allow for easy transfer of electrons away from the nucleus • Tightlybound to the nuclei http://glassian.org

25. Concept 2 – Energy Transfer • In a conductor the electrons are more loosely bound so they can move away from the nuclei • Current will only flow if the conductor is hooked to an electrical source www.diy-guides.com www.copper.org

26. Concept 2 – Energy Transfer • Different materials conduct electricity at different abilities • Important to know so devices designed are both safe and effective www.mutr.co.uk

27. Concept 2 – Energy Transfer • A resistor is a type of conductor • Allows current to pass but applies a resistance to it • Limits amount of electric current to pass • Resistance is a measure of how difficult it is for electrons to flow through a substance www.yksd.com

28. Concept 2 – Energy Transfer • Resistance is measured in ohms • Symbol is the Greek letter omega, W • The more resistance a substance has, the more energy is gained from each electron passing through it www.electronicsandyou.com

29. Concept 2 – Energy Transfer • A polygraph machine (lie detector) is an application of resistance • Measures skin resistance, blood pressure and respiration www.mentalfloss.com

30. Concept 2 – Energy Transfer Learning Concept • Use switches and resistors to control electrical flow • Predict effect of these devices and others in an application

31. Concept 2 – Energy Transfer • A switch is the best method for turning electricity on and off • Basic principle: when on, two conductors are pressed together and electrons can flow • When off, the conductors are not in contact, and electron flow is interrupted www.web.net www.edupic.net

32. Concept 2 – Energy Transfer • A variable resistor, or rheostat, is used to increase or decrease the amount of current in a circuit slowly • Dimmer light switch • Volumes on stereos • Foot-operated speed controls on sewing machines

33. Concept 2 – Energy Transfer Learning Concept • Describe, using models, the nature of electric current • Explain the relationship between current, resistance, and voltage

34. Concept 2 – Energy Transfer • Recall: • Current looks at how quickly an electrical charge is able to move (amps) • Voltage looks at how much charge is carried in the electrical current (volts) • Resistance is a measure of how difficult it is for electrons to transfer (ohms) www.websters-online-dictionary.net

35. Concept 2 – Energy Transfer

36. Concept 2 – Energy Transfer • The hydo-flow model has several components • Water in the container • Amount of water pouring from the spouts • Force of gravity on the water • Diameter of the spout

37. Concept 2 – Energy Transfer Learning Concept • Measure voltages and amperages in circuits • Apply Ohm’s law to calculate resistance, voltage and current in simple circuits

38. Concept 2 – Energy Transfer • German scientist Georg Simon Ohm proved a mathematical link between voltage (V), current (I) and resistance (R)

39. Concept 2 – Energy Transfer • Ohm’s law states that as long as temperature remains the same • Resistance of a conductor stays the same • Current is directly proportional to the voltage applied www.sengpielaudio.com

40. Concept 2 – Energy Transfer • So long as two of the three units are known, the last one can be solved for http://cyberchalky.files.wordpress.com

41. Concept 2 – Energy Transfer

42. Concept 2 – Energy Transfer Example • An electrical stove is connected to a 240-V outlet. If the current flowing through the stove is 20-A, what is the resistance of the heating element?

43. Concept 2 – Energy Transfer Example • A 30-V battery creates a current through a 15-Ω resistor. How much current is created?

44. Concept 2 – Energy Transfer Example • A motor has an internal resistance of 40-Ω. The motor is in a circuit with a current of 4.0-A. What is the voltage?

45. Concept 2 – Energy Transfer Example • A current of 625-mA runs through a bulb that is connected to 120-V. What is the resistance of the bulb?

46. Concept 2 – Energy Transfer Learning Concept • Develop, test and troubleshoot circuit designs for a variety of specific purposes

47. Concept 2 – Energy Transfer • A circuit is simply a complete path that charged particles can flow through • Often drawn with symbols in an image known as a schematic or a schematic diagram www.bin95.com

48. Concept 2 – Energy Transfer • Using your textbook as a reference (pg 312) complete the following diagram of electrical symbols

49. Concept 2 – Energy Transfer • A series circuit is one in which the current passes through each bulb in turn www.electronicsandyou.com

50. Concept 2 – Energy Transfer • Disadvantages • If the pathway is interrupted the whole circuit cannot function • Adding components increases the total resistance • Adding another bulb would make all the lights dimmer www.sciencephoto.com/