MITES Middle School Introduction To Engineering Systems

Transcription

1 MITES Middle School Introduction To Engineering Systems

2 2 Expectations for Behavior Be Respectful To teacher, To Peers, To Facilities Follow 1 st Request From Teachers or Peers Golden Rule Treat others the way you want to be treated

3 3 Engineering Engineering is the discipline, skill, and profession of acquiring and applying scientific, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes. Electrical Civil Mechanical Aerospace

4 Engineering Design Process 4

5 Lab Safety Concerns 5

6 6 The Ultimate Goal - Presentation Mechanical/electrical energy; Motors/generators Electricity and magnets Electric motor Electromagnetic generator Solar energy and panels Solar buzzer & open/closed circuits Solar car and motor Windmill and wind energy

7 7 Every Group Must Make a Poster ~7 minutes per group Define or Demonstrate important terms or materials Why is it important to understand these concepts Describe how the concept or technology works Give examples of application (use your microgrid and/or real world examples)

8 Forms of Energy Electromagnets Motors vs. Generators

9 9 Objective of the lesson Review forms of Energy? Check understanding of simple vocabulary? Describe a simple circuit. Compare Magnetic field and Magnetic Force. Review Battery operation. Compare electric motors and generators. Build a simple motor!

10 10 Reviews the Forms of Energy Potential Kinetic

11 11 Vocabulary Can you tell me what these are? Electron Proton Electrical Conductor Electrical Insulator

12 12 Matter and atoms All matter is made of atoms. Structure of an ATOM All atoms are made up of electrons, protons and neutrons. Protons and neutrons form nucleus. Electrons orbit around the nucleus.

13 Law of Electric Charges Same charge repel Opposite charge attract (similar to magnets) Objects can become charged by friction, conduction, and induction.

14 14 Conductors and Insulators Conductors are a material which contains movable electric charges. Almost all metals such as gold, silver, copper, iron, and lead are good conductors. Polymer, glass, paper, wood or Teflon are very good electrical insulators

15 Insulators and Conductors Have you ever noticed that electrical cords are often made from metal and plastic? Why? What is the most common material used in wires?

16 16 MORE Vocabulary Simple Circuit Electrical Current (I), amperes (A) Voltage (V), volts (V) Resistance (R), ohms (Ω) Power (P), watts (W) Electric Force Electric Field

17 Electric Circuit Circuit diagrams are a pictorial way of showing circuits. Electricians and engineers draw circuit diagrams to help them design the actual circuits. 17

18 Components of Electric circuit Circuit component Electric Source Definition Source of electric energy/current Examples Battery, Solar cell, Electric generator, Electric Load Switches Measuring devices anything that uses/absorbs the energy that is being delivered by the electric current in a circuit A device that connect circuit /allow flow of electrons when on Measure current, voltage and power Lamps, fan, washing machine, computer, Resistance Electronic switches, Mechanical switch Ammeter, Voltmeter, wattmeter 18

19 19 Symbols the Ammeter Voltmeter resistor Switch battery Light bulb Light bulb

20 Current Electricity Moving charges/electrons Current electricity is controlled movement of charges through a path, usually a conductor of electricity.

21 This is a strong current! 21

22 22 Current (I) Current is the rate at which charges pass a given point Similar to water flow in a hose Units : amperes, amps. Symbol for ampere : A. The symbol for current is the letter I.

23 Voltage (V) Voltage= Potential difference= Pressure difference in water hose Units: Volts Measured by a voltmeter Voltmeter connected always across/parallel Measurement of Electromotive Force (remember this) Voltage in your house? Voltage of AA batteries? An electric eel can create a voltage of more than 600 V!

24 Resistance 24

25 25 Resistance and Ohm s Law R = V/I or V = R x I

26 26 Do some simple math Using Ohm's Law What is the voltage if the current is 2 A and the resistance is 12 Ω? Step 1: Write the equation for voltage. V = I R Step 2: Replace the current and resistance with the measurements given in the problem, and solve. V = 2 A 12 Ω V = 24 V

27 27 You try it! Find the voltage if the current is 2 A and the resistance is 2 Ω. The resistance of an object is 10 Ω. If the current in the object is 2 A, what voltage must be used?

28 28 Electric Power the rate at which electrical energy is converted into other forms of energy power = voltage current, or P = V I

29 A Little more math! Power and Energy A small television set draws a current of 0.42 A at 120 V. What is the power rating for the television? How much energy is used if the television is on for 3 h? Step 1: Write the equation for power. P = V I Step 2: Replace the voltage and current with the measurements given in the problem, and solve. P = 120 V 0.42 A P = 50.4 W, or kw 29

30 Power and Energy A small television set draws a current of 0.42 A at 120 V. What is the power rating for the television? How much energy is used if the television is on for 3 h? Step 3: Write the equation for electrical energy. E = P t Step 4: Replace the power and time with the measurements given in the problem, and solve. E = kw 3 h so E = kwh 30

31 31 Your turn again! A computer monitor draws 1.2 A at a voltage of 120 V. What is the power rating of the monitor? How much energy is used in 3 hours. At $8.65/kWh, how much did it cost to run run the computer monitor? P = V x I And E = P x t

32 Electric Field 32

33 33 Electric Force

34 Making an Electromagnet 34

35 Electromagnetism Magnetism is a result of electrons spinning on their own axis around the nucleus (electromagnet principle) So an external magnetic field will have an effect on electrons in that field. If the field moves, the electrons in it will try to move and thus cause a current nucleu s

36 How to generate electricity? Law of Energy Conservation?? Energy can neither be created or destroyed. It changes from one form to another Direct Energy conversion to Electricity a) From Chemical energy ( Example: Batteries, fuel cells) b) From mechanical energy and magnetic energy (Generators) c) From light energy (solar panels) d) From thermal energy (Thermocouples) e) From biomass( Electric eel )

37 37 Cell/Batteries Anatomy Electrodes- Cathode: Positive terminal Anode: negative terminals Electrolyte- Acid(Lead-acid battery) Alkaline (Alkaline batteries)

38 How a cell works. 38

39 39 How a Generator works! Electromotive Force creates Electromagnetic Induction

40 Generating Electricity Faraday's Law: Electric force is generated due to a changing Magnetic -field through a conducting coil, also called principle of induction. Moving magnet, stationary coil Moving coil, stationary magnet

41 Faraday s Law Voltage generated proportional to 1. Number of coil turns, N 2. Strength of the magnets 3. change in magnetic field a) Speed of rotation Approximate pull force: over 12 lbs Approximate pull force: over 4.5 lbs Speed= 1 rotation/sec Vgen= 8 volts Speed= 2 rotation/sec Vgen= 16 volts

42 42 How a motor works! Look familiar! Why does an electric motor do what it does?

43 43 Mnemonic for Electric Motors

44 Activity Build a Motor Materials needed Three ring-shaped magnets Insulated wire (about 4 feet is needed) Wire cutters / strippers One D-size battery Two large paper clips Tape Click here for the procedure.

45 45 References Woodford, Chris. (2007) Electric Motors. Retrieved from [Accessed 6/2012] Museum of Science and Industry, Chicago. (2012) Retreived from [accessed 6/2012] Guard, John. 1 Star Drive. [accessed 6/2012]