1. Lightning occurs when large amounts of electric charge flow between the clouds and the ground a

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Cases – Chapter 10

1. Lightning occurs when large amounts of electric charge flow between the clouds and the ground.

a. Lightning is most likely to strike when a cloud and the ground beneath it have accumulated large opposite charges. Why is lightning unlikely when they have large like charges?

b. The atmosphere does a great deal of work in creating the separated charge that produces lightning. Show that it takes work to move positive charge from the negatively charged ground to the positively charged cloud overhead.

c. When enough opposite charge has accumulated on the ground and in the cloud above it, lightning will strike. One indication that this dangerous charge accumulation has occurred is that your hair begins to stand up. Explain this effect.

d. A sharp lightning rod reduces any local build-up of electric charge and prevents nearby lightning strikes. How does the lightning rod get rid of local electric charge and allow it to flow gradually to the clouds overhead?

2. A Van de Graaff generator is an electrostatic device that uses a moving nonconductive belt to carry electric charge into a hollow metal sphere. This sphere is insulated from the ground and can accumulate charge until enormous voltages are reached. Small Van de Graaff generators are exciting novelties while large ones are used in research and industry.

a. A typical Van de Graaff generator uses a rubber belt to carry negatively charged electrons from its base to the sphere. As the belt passes through the sphere, a metal brush touches it. Electrons leave the belt and flow through a wire to the surrounding sphere. Why do they flow onto the outside of the sphere rather than staying near the belt?

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