7th Grade Test Prep Quiz #3

Why does the author most likely place the information in paragraphs 1–2 at the beginning of “Energy Story”?

1 Electricity figures everywhere in our lives. Electricity lights up our homes, cooks our food, powers our computers, television sets, and other electronic devices. Electricity from batteries keeps our cars running and makes our flashlights shine in the dark. 

2 Here’s something you can do to see the importance of electricity. Take a walk through your school, house or apartment and write down all the different appliances, devices and machines that use electricity. You’ll be amazed at how many things we use each and every day that depend on electricity. 

• to encourage the reader to learn how electronic devices are made

• to show the reader how different machines can improve our lives

• to draw the reader in by showing how electricity affects everyone

• to teach the reader how to use electricity in different settings

Which detail from “Energy Story” best supports the answer in Part A?

• “. . . walk through your school, house or apartment . . .” (paragraph 2)

• “. . . how many things we use each and every day that depend on electricity.” (paragraph 2)

• “. . . in the same way the moon spins around the earth.” (paragraph 5)

• “. . . each person would have a bucket of water to pour from one bucket to another.” (paragraph 12)

Which sentence best states the central idea of paragraphs 21–22 in “Energy Story”?

21 Electricity is conducted through some things better than others. Its resistance measures how well something conducts electricity. Some things hold their electrons very tightly. Electrons do not move through them very well. These things are called insulators. Rubber, plastic, cloth, glass and dry air are good insulators and have very high resistance. 

22 Other materials have some loosely held electrons, which move through them very easily. These are called conductors. Most metals—like copper, aluminum or steel—are good conductors. 

• Materials that are insulators and conductors have a high resistance to electricity.

• It is more difficult for electricity to pass through insulators than conductors.

• Insulators and conductors are able to generate a high amount of electricity.

• Electrons move through rubber easier than they move through metal.

Which sentence from “Energy Story” best supports the answer in Part A?

• “Electricity is conducted through some things better than others.”

• “Its resistance measures how well something conducts electricity.”

• “Some things hold their electrons very tightly.”

• “Other materials have some loosely held electrons, which move through them very easily.”

Which phrase is closest in meaning to the word deliberately as it is used in paragraph 3 of “Short Circuit”?

What’s Going On? 

3 The thin iron wire is a good conductor of electricity, but not as good as the copper wire, which is deliberately chosen to have very low resistance. Thus, most of the resistance of the circuit is in the iron wire. When you connect the clip to the iron wire, the voltage of the battery pushes electrons through the circuit against the resistance of the iron wire, causing the iron wire to heat up. As you move the clip closer to the battery, the resistance of the iron wire decreases. Because the same voltage is applied across a lower resistance, more current flows, and the wire heats up more. Eventually, when you make the iron wire short enough, so much current flows that it melts the wire. Even the copper wire becomes warm. 

• for the most part

• by general agreement

• with short notice

• with careful consideration

Which detail from “Short Circuit” provides the best clue to the meaning of the word deliberately?

• “good conductor”

• “not as good”

• “chosen to”

• “very low”

Which sentence best states a central idea of “Short Circuit”?

• Appliances can be destroyed by a heavy flow of electrons.

• The flow of electrons follows a path of least resistance.

• Fuses are an important means to keep homes safe from electrical hazards.

• Circuit breakers are a tool to control the flow of electricity in homes.

Which detail from the article provides the best example of the central idea in Part A?

• “In a normal electric circuit, an electric current powers an appliance, such as a refrigerator or TV.”

• “Every such appliance has a certain amount of resistance to the current flow, which keeps the current from reaching very large values.”

• “Although houses today often contain circuit breakers rather than fuses, fuses are still around.”

• “. . . the wire in the fuse heats up quickly and melts, breaking the circuit and preventing a fire from breaking out.”

Which step of the experiment is repeated multiple times in “Short Circuit”?

• Use an alligator clip to attach a copper wire to a battery terminal.

• Attach one end of an iron wire to the other battery terminal.

• Use a second alligator clip to attach the other end of the copper wire to the iron wire.

• Shorten the distance between the second alligator clip and the battery.

A result occurs when the step is repeated in the experiment. Which phrase from “Short Circuit” shows the result of the repeated step that is the answer to Part A?

• “. . . deliberately chosen to have very low resistance.”

• “. . . voltage of the battery pushes electrons through the circuit . . .”

• “. . . more current flows . . .”

• “. . . which keeps the current from reaching very large values.”