READ
PREVIEW
1. There are two types of electrical current: AC and DC. What do you already know about them?
2. The differences between AC and DC caused a big competition between businesses. Some people preferred AC power; others preferred DC power. Think of other inventions. Which have had similar beginnings? Think of other products where you must choose one type or another type.
3. In the U.S., most electricity comes from a "utility". A utility is a kind of company. It provides basic things. What other things come from a utility?
VOCABULARY TO KNOW BEFORE YOU READ
current (noun) - the flow of electricity through a wire
require (verb) - to need something or to make something necessary
transformer (noun) - a piece of equipment that changes the strength of an electrical current
THINK ABOUT THE WORD "DEMONSTRATE"
Here are some of the definitions from Cambridge Learner's Dictionary:
| Verb | Noun |
| to prove that something exists or is true | proof that something exists or is true |
| to show someone how to do something, or how something works | an occasion when someone shows how to do something, or how something works |
| to march or stand with a group of people to show that you disagree with or support someone or something | an occasion when a group of people march or stand together to show that they disagree with or support someone or something |
What is the same? What do these definitions have in common?
Sample Answer
✔ All the definitions have something to do with showing or proving something to others.
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