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Electricity and Circuits

Electricity and Circuits. Engineers in Training Day 2. Developed by Shodor and Michael Woody. Electricity. What uses electricity? Name some things that use electricity Try to name something you like to do that doesn’t use electricity.

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Electricity and Circuits

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  1. Electricity and Circuits Engineers in Training Day 2 Developed by Shodor and Michael Woody

  2. Electricity • What uses electricity? • Name some things that use electricity • Try to name something you like to do that doesn’t use electricity. • Everything that uses electricity is made up of at least one circuit • To figure out how we use electricity we first will look at water.

  3. Waterwheel • Suppose we want to grind some grain using a water wheel • What do you need to have a water wheel? • Water • Hill (for the water to flow down) • Pipes/channels (to direct the water) • The water wheel (to power something) • Mill, pump, etc (something needing power)

  4. Waterwheel

  5. Three Important Measures • What things might we measure about our water wheel setup? • How high/steep is the hill? • How fast is the water moving? • How much grain can we grind every day?

  6. What about Circuits? • Our circuits are very similar to waterwheels. • Instead of a landscape we have a breadboard • This is where we put our circuit together

  7. What about Circuits? • Our circuits are very similar to waterwheels. • We have electric charge instead of water • This is what makes everything go in the circuit

  8. What about Circuits? • Our circuits are very similar to waterwheels. • And a battery instead of a hill • Without this the charges wouldn’t move, they would just stand still and do nothing.

  9. What about Circuits? • Our circuits are very similar to waterwheels. • Wires for pipes and channels • These carry the electricity to where we want to go and direct it

  10. What about Circuits? • Our circuits are very similar to waterwheels. • A light bulb (or motor, etc.) that needs power instead of the water wheel. • This is the end goal of our circuit, to accomplish some task.

  11. Terminology • Voltage (potential) • This is like the height of our hill • The more voltage, the more the electricity wants to move • We measure this in Volts (V) • High voltage means more electricity (charge) will go through a wire

  12. Terminology • Current (rate of flow) • This is like amount of water flowing • Current measures how much electricity is moving through a wire • This is measured in Amperes or Amps (A) • High current means a lot of electricity is moving (high current is very dangerous)

  13. Terminology • Power • This is how much work our circuit does • Corresponds to how much grain is milled, etc. • Measured in Watts (W) • High Power = lots of work which can mean heat. • 100 W light bulb is hotter and brighter than 60W.

  14. Lets Build a Circuit • We are going to build a circuit together now. • We will use the battery, the breadboard, the resistor, and the LED to make the LED turn on.

  15. Breadboard • Breadboards are used to connect things quickly • You can proto-type circuits quickly

  16. How to use your Breadboard • This diagram shows what holes are connected to each other. • You connect things together by plugging them in to holes connected to each other

  17. Parts of Our Circuit • Battery • Source of constant potential (9 V)

  18. Parts of Our Circuit • Wires • We have wires connected to our battery. + lead (red wire) – outflow from high potential - lead (black wire) – inflow to low potential

  19. Parts of Our Circuit • Light Emitting Diode (LED) • Emits light when current flows through it • Current can only flow in one direction, from + to - (like a water wheel that won’t go in reverse) • Long lead (+) • Short lead (-) • Can be damaged by high current

  20. Parts of Our Circuit • Resistor • Will keep our LED from getting damaged by too much current. • New term: • Resistance – how easy is it for current to flow • Symbol (R) • Unit (Ohm – Ω) • Circuit element • Resistor, like a wire • Regulates the flow of current • The higher the resistance the less current will flow • Current = Voltage/Resistance

  21. Lets Build a Circuit • Use the battery, the breadboard, the resistor, and the LED to make the LED turn on. • Follow the “LED Circuit” in your handout. • Watch for polarity (plus minus signs) especially for the LED • Why is the resistor necessary?

  22. Take a Break • When we come back we’ll look at some more electronic components and build a more complex circuit

  23. Exercise • Go to http://falstad.com/circuit/ • Choose Circuits → Basic → Ohm’s Law • Ohms Law: V= I x R or I = V/R • In which branch will more current flow? • Imagine a networks of pipes

  24. Capacitor • Like a glass that holds water • The more electricity flows in, the higher the voltage (water level) • It will eventually ‘fill up’ with electricity • A large capacitor is like a wide glass • Needs more water (electricity) to get to the same height (voltage) • For same voltage and resistance of the circuit, it will take longer to fill all the way up

  25. 555 Timer Chip • Used to oscillate between a high (+5V) and low (0V) voltage • Stays high until the Threshold input rises above a certain level, then switches low and lets the attached capacitor start to discharge. • Stays low until Trigger falls below another level, then switches high and stops the capacitor from discharging.

  26. Exercise • Go to http://falstad.com/circuit/ • Choose Circuits → 555 Timer Chip → Square Wave Generator • Build the circuit shown • Use the output to power the LED Circuit from first exercise • “555 Timer Circuit” in your handout gives the circuit, for convenience

  27. The Circuit • The 555 timer will switch the output back and forth as the capacitor charges and discharges. • Before trying both capacitors, which one will make the light blink faster?

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