1. Environment and teaching kits Andrzej Kotlicki Physics and Astronomy

2. Voltage, Current, Resistance, Power R = V/I P =IV = V 2 /R = I 2 R

3. Multimeters Measuring voltage current resistance: Precautions Measure resistance outside the circuit Multimeters have resistance in the order of mega ohms when measuring voltage and resistance in the order of ohms/ milliohms when measuring current. When measuring resistance, the multimeter acts as a power source – to measure the resistance of a component (light bulb, resistor …), you must take it OUT of the circuit first! Current fuse – when it burns? Warning: Do NOT connect multimeter in parallel with source when measuring current! The fuse will burn and it will need to be replaced before you can measure current again.

4. SOLDERLESS BREADBOARD

5. Breadboard (design board) – connections between the holes are shown in red – Use only the specified wire

6. Light Emitting Diodes LEDs – voltage –current characteristics: They only work in one direction They will be destroyed if a too high voltage is applied (in any direction)!

7. Light Emitting Diodes LEDs – example circuit – In principle we need a current source, very often IC – flip directions if LED doesn’t light up 9V 360 A resistor of high enough resistance is necessary in the circuit to reduce the voltage across the LED. This keeps the LED current from exceeding its maximum value and burning The typical voltage across the LED is about 3 V, and the typical current for a small LED is ~ 10 mA. So to calculate the resistance (in ohms), subtract 3V from the voltage of the battery, and divide the difference by the current (in amps).

8. Solar Panels How they work? – http://c21.phas.ubc.ca/article/solar-energy-how-do- photovoltaics-work Power – notice that both voltage and current changes with light intensity Maximum power and load – You can optimize the power delivered to the load by changing the resistance of the load in the circuit (e.g., if the load is just a resistor, you can adjust its resistance to have maximum power. You can show this in a classroom activity using the panel with a variable resistor and multimeters)

9. Gearbox Purpose Role in wind and water turbines. – Gearboxes are a necessary component of wind and water turbines, to make generators spin fast enough to produce electricity Our little crank turbine – In the workshop, we compared the feel of three different gear ratios. The higher the ratio -> harder to turn the crank, faster resulting spin and therefore higher voltage generated by the motor. – The resistance of the crank to turn may also depend on the load. You can see this with a medium gear ratio, spinning the crank fast and letting go, with an LED then an incandescent light bulb. The crank stops turning much faster when connected to the incandescent.

10. Light sources Incandescent Fluorescent and low voltage (12V) fluorescent – Interesting note: Low voltage fluorescents (e.g., for use in boats, automobiles) are not much more efficient because their accompanying electronics convert the DC (direct current) power source to high voltage AC (alternating current) LED – LEDs, if used properly, will last you a lifetime Efficiency of different light sources – Most of the energy going into incandescent lights produces infrared radiation (heat). Also, the fluorescent light with its accompanying electronics uses more energy per unit of luminance than LED Spectrum – A current problem: researchers are working on making the spectrum from LEDs more and more like natural light Coming ways of illuminating – With the new LED fixtures, we would not need any mechanics to change the sources (screw in bulbs) – Because LEDs are good point sources, it is much easier to direct light to the area which needs a particular level of illumination

11. Kill-a-Watt meter Use. Example with 3 kinds of lights of the same intensity – Kill-a-watt meters measure power consumption. They can be used in the classroom to compare 3 kinds of lights with the same light intensity (“60 W equivalents”). – They are also handy around the house to identify hidden sources of power consumption. For example, transformers/ battery chargers can consume power even when no device is plugged in

12. Issues with green electrical power Solar, wind and hydro Nuclear Why we use AC? What is AC The implications for the grid Global grid? – would solve the problem of intermittent energy production by solar, wind generators (we always have some sun in some part of the world.) DC power lines? Superconducting power lines?