1. Develop a concept map encorporating the following concepts we have discussed in this class: (a) electric field, (b) current, (c) resistance, (d) potential difference, (e) battery, (f) electric potential energy, (g) electric power.  Show as many relationships between the concepts as you can. Use examples if they help to explain your relationships.  You may wish to start with subsets of these concepts. Some suggested subsets: a-b-c, c-d-e, b-d-f, d-f-g.
 

2. Batteries are always labeled with their emf; for instance, a AA flashlight battery is labeled "1.5 volts." Would it also be appropriate to put a label on batteries stating how much current they provide? Why or why not? What sort of current information might be appropriate?
 

3. Sharks can detect electric fields as weak as 1 microvolt/meter, which is in the range of the electric fields found along the skins of animals (in particular that of the fish the shark wants to eat!). The organs that can detect such weak fields are called the ampullae of Lorenzini. These are jelly-filled tubes that are many centimeters long but only a millimeter or two in diameter. One end of the tube opens at the surface of the shark's head. The walls of the tubes and the skin of the shark have high resistivity, but the resistivity of the jelly is quite low. How do you suppose the ampullae of Lorenzini function?
 

4. Make an analogy between flow of water in a house and flow of electrical current in a wire? What role does water pressure in the plumbing serve? A shut-off valve? A vertical run of pipe? Different diameters of pipe?
 

5. You are an electrician working on building a house. The instructions for connecting a wire to an outlet recommend that the wire be wrapped at least three-quarters of the way around a terminal post. The general contractor wants you to save money by only wrapping half-way around the post. Explain the consequences of this request to the contractor.
 

6. Which 120-Volt bulb has the greatest resistance in its filament, a 60-Watt bulb or a 120-Watt bulb? Assuming the two filaments have equal length and are made of the same material, which filament is thinner?
 

7. You have a friend who recently bought an electrical space heater for his dorm room. The heater is rated at 1000 Watts and is designed to operate on a 240 volt circuit. Unfortunately for your friend, his dorm room is only equipped with 120 volt outlets. For this problem, assume these voltages are direct current (dc) rather than alternating current. What is the resistance of the space heater? If your friend goes ahead an plugs it into an outlet in his dorm room, what power output (dissipated as heat) will he get from his heater?
 

8. A table lamp is connected to an electric outlet by a copper wire 2mm in diameter and 2m in length. Assume the steady (DC) current through the lamp is 1.5A. How long does it take an electron to travel from the outlet to the lamp?