Critical Thinking

22. Applying Concepts In a science museum demonstration, a person on an insulated stand touches a metal sphere. The sphere has a large charge. Explain why the person's hair stands on end.

23. Applying Concepts Explain why a battery is always connected so that one wire goes to the battery's positive terminal and one to the negative terminal.

24. Relating Cause and Effect A person plugs a fan into a wall socket and turns it on. Suddenly, the lights go out in several rooms of the house. Explain what has probably happened and what can be done to fix it.

25. Applying Concepts Explain why a hair dryer has a high-heat setting with a lower resistance than the low-heat setting. (Hint: Use the equation $P\mathit{ }\mathit{=}\mathit{ }IV\mathit{.}$)

26. Comparing and Contrasting How are n-type semiconductors and p-type semiconductors alike. How are they different?

Math Skills

27. Calculating On a wet day, your skin's resistance may be as low as 1000 ohms. On a dry day, it may be as high as 100,000 ohms. How much current moves through your fingers if you touch the terminals of a 9-volt battery on a wet day? On a dry day?

28. Calculating Six light bulbs are connected in series with a 9.0-volt battery. What is the voltage across each bulb?

29. Calculating A freezer has a power rating of 105 watts. How much current does it use if it is plugged into a 120-volt line?

30. Calculating The power rating on an electric oven is 9300 watts. If the oven is plugged into a 240-volt line, how much current does it use? What is the resistance of the oven?

Concepts in Action

31. Relating Cause and Effect You turn a television on and notice a faint crackling sound. If you touch the screen, you get a small shock. What is the source of this electric charge?

32. Inferring Plugs used for connecting an electrical appliance such as a toaster to a wall socket have two prongs. Explain why plugs have two prongs instead of one prong.

33. Inferring The photograph below shows ceramic insulators holding the power lines at each pole. What is the purpose of the insulators?

    

34. Making Judgments Explain why you think builders should or should not be required to install GFCI (ground-fault circuit interrupter) outlets in all new homes.

35. Writing in Science Write a paragraph explaining in detail why you could be struck by lightning if you stand outside during a thunderstorm. Include a sketch that illustrates the ideas in your paragraph.

Performance-Based Assessment

Designing an Experiment Design and conduct an experiment that uses a light-emitting diode in a simple circuit to demonstrate that current flows only one way through a diode. Before beginning, research the properties and limitations of your diode.

Table of Contents