1. Designed Learning Joel Rosenberg Chapter 28

2. Summary Joel Rosenberg, a curriculum developer who helped create this course, Discusses some of the water models he has used to understand circuits Discusses some of the air models he has used to understand circuits as an analogy for flowing charge. Introduces Ohm’s law, which is a statement about the relationship between voltage, current, and resistance. Discusses the relationship between voltage, current, and power.

3. Electricity and Electronics Electricity is what we call the charge flowing in wires. Electronics is the way we control that electricity to accomplish tasks.

4. Electric pressure difference An electric pressure difference causes charge to flow from a region of higher electric pressure to a region of lower electric pressure Electric pressure difference is often referred to as voltage. The unit is the volt.

5. Current Current is the flow rate of charge moving through a circuit. The unit for current is the ampere, or amp.

6. Resistance Resistance is the opposition to flow experienced by the current. The components of a circuit – the conductors and the load – offer resistance. The unit for resistance in electrical systems is the ohm.

7. Ohm’s law

8. Power

9. Question 1 Question Joel’s early model of electricity used water as an analogy for charge. His current model uses air as an analogy. Why does he think air is a better analogy? Answer Air is compressible, but water is not. It flows from a region of higher pressure to a region of lower pressure, which is similar to electric charge.

10. Question 2 Question There are extensive electrical grids that distribute electricity from power plants to our homes. The long distances the electrical charge must move creates extremely high resistances, so very high voltages are used. Use what you’ve learned about the relationship between voltage, current, and resistance to explain why high voltages might be used to move an electrical charge through the distribution grid. Answer Given Ohm’s law, a very high resistance would mean a very low current. So, to keep a measureable current flowing, the voltage also must be very high.