5CK) MAGNETISM AND ELECTRIC I IN ^A/\^ Ri Ra ¥lG. 237. Series wiring. -AA/\^ ^ AW^
CURRENT ELECTRICITY 501 ance. In such a string all the lights go out when one light goes out because the flow of current is broken at this point. Lights in ordinary house-lighting circuits are wired in parallel, thus enabling one light to be turned off without affecting the others. If such lights were wired in series, the light in each bulb would grow dimmer for each added bulb, because the added resistance would decrease the amount of current flowing. Fig. 240. Cells are generally connected in series; Cells are usually connected in series. the voltage of the series is equal to the sum of the voltages of each of the individual cells. STUDY QUESTIONS 1. What Is the nature of an electric current? 2. Differentiate between direct and alternating current. 3. Use the water analogy in explaining the flow of an electric current through a conductor. 4. Describe the original observations that led to the first chemical cell. 5. List the different combinations of metals and electrolytes that will produce an electric current. 6. State Ohm's law. Give an application of this law. 7. Name the electrical unit of measurement for each term in Ohm's law. 8. In what units is electrical power sold? What is the meaning of these units? 9. Differentiate between series and parallel wiring. When is series wiring desirable? 10. How much would it cost to operate an electric iron that uses 6 amperes of an ordinary 110-volt current for 24 hours if the electrical power sells for 6 cents a kilowatt-hour? 11. What is the resistance of a 110-volt electric toaster that has a rating of 600 watts? How much would it cost to operate the toaster for 3 hours if the power costs 12 cents a kilowatt-hour? How long could a 50-watt lamp be operated for the same amount? 12. Is resistance a property of electricity or of a conductor? 13. Explain how one can connect severak conductors so that their combined resistance will be less than the sum of their individual resistances. 14. What type of electrical household appliances cost the most to operate? 15. Give the main facts of current electricity. 16. Give the laws of current electricity. 17. Give the theory that explains the laws and facts of current electricity. 18. Try to apply Ohm's law to some other type of energy. 19. Why is it that electricity will not flow to an object but has to flow through the object if the current is to flow at all?