Unit 6: Forms of Energy

Min tapes a piece of string to each of two ping-pong balls. He hangs the balls so that they are close to one another but do not touch. Later, he finds that they have pulled together. They are now touching. What reasoning could explain why the two balls are now touching?

• They have both lost their charges.

• They have gained opposite charges.

• They have both gained a positive charge.

• They have both gained a negative charge.

Curtis uses a wool cloth to give a balloon a negative charge. Which claim and reasoning describes what will happen when he holds the balloon near the wall, and why?

• The balloon will stick to the wall because a negatively charged object is attracted to an uncharged object.

• The balloon will stick to the wall because a negatively charged object is attracted to another negatively charged object.

• The balloon will not stick to the wall because a negatively charged object is repelled by an uncharged object.

• The balloon will not stick to the wall because a negatively charged object is repelled by another negatively charged object.

Aisha wanted to know how positive and negative charges affect balloons. The balloons shown below are part of her investigation. What are the charges on the balloons?

• They are both positive.

• They are both negative.

• They are both uncharged.

• One is positive, and one is negative.

What form of energy cooks food in a solar cooker?

• chemical energy

• electrical energy

• light energy

• mechanical energy

To conserve energy or if they don’t have a clothes dryer, some people hang their laundry outside to air dry. Which of the following is the most optimal day to hang laundry?

• a cold, rainy day 

• a cold, cloudy day

• a warm, sunny day

• a warm, cloudy day

An electron is the particle most easily removed from an atom. What is the electric charge of a neutral atom from which an electron has been removed?

• negative

• neutral

• nucleus

• positive

Why do two socks sometimes stick together in a dryer?

• Both socks have a positive charge.

• Both socks have a negative charge.

• Protons move from one sock to another.

• Electrons move from one sock to another.

Which is true about how a charged object interacts with a neutral object?

• The charged object becomes uncharged.

• The neutral object remains neutral.

• They repel each other.

• They attract each other.

In a three-pronged plug, one flat prong carries current from the supply that enters the electrical outlet, and the other returns the current to the service panel of the building. The round prong helps protect people from electrical shocks. What has a purpose similar to that of the round prong?

• a magnet

• a generator

• the plug's plastic covering

• the holes in the flat prongs

A material that allows an electric current to flow through it is an electrical conductor. A material through which an electric current cannot flow easily is called an insulator. Which claim best describes the difference between an insulator and a conductor?

• An insulator has a static charge, and a conductor does not.

• A conductor contains more electrons than an insulator.

• A conductor is a metal, and an insulator is any material that is not a metal.

• An insulator does not have electrons that are free to move, and a conductor does.