Electromagnetic Forces CAST

Two plastic cups are placed 25 cm apart. What factors determine the strength of the electric field between these two cups? Select all that apply.

• the charge on Cup A

• the charge on Cup B

• the distance between the cups

• whether the cups are insulators or conductors

What phenomenon is the student investigating?

• Photosynthesis

• Evaporation

• Magnetism

• Condensation

The amount of potential energy within a system changes when the arrangement of objects within that system changes. Which of the actions below could a student use to model a change in gravitational potential energy of a system? Select all that apply.

• A) Moving a book from one shelf to another on a bookshelf

• B) Stretching a slingshot to fire a pebble

• C) Changing the mass of a car rolling across the floor

• D) Lifting a weighted bar from waist height to over the head

• E) Placing a skateboard at different points on a steep hill

A student built an electric motor from a D battery, a wire coil made from wrapping an insulated wire 10 times around the battery, two safety pins, a rubber band, and some magnets. The student recorded the data in the table below. What question was the student trying to answer with this experiment?

• How does the number of magnets affect the strength of an electric motor?

• How does the number of magnets affect the speed of an electric motor?

• How does an electric motor affect the strength of a magnet?

• How does an electric motor affect the magnitude of a magnetic field?

You have been given two magnets and a paper clip. Use these materials to design an investigation into the strength of a magnetic field. Think about how magnets interact with objects like paper clips. Visualize the forces at play as you design the experiment. How do metallic objects interact with magnets, and how can you use that interaction to provide evidence of the magnitude of each magnet's magnetic field?

• Design an experiment to measure the distance at which each magnet can attract the paper clip.

• Explain how the paper clip can be used to measure the weight of the magnets.

• Describe how to use the magnets to create an electric current.

• Discuss how to use the paper clip to determine the temperature of the magnets.

In this performance task, you will apply your knowledge of electromagnetic and magnetic interactions. A student wants to learn about electromagnetic and magnetic forces and will conduct two investigations to better understand these forces. The first investigation involves building an electromagnet, and the second investigation involves observing interactions between two bar magnets. Electromagnet Investigation: The student is given a D-cell battery, a rubber band, an iron nail, and a copper wire. The student constructs an electromagnet by wrapping the wire around the nail and connecting the wire to the battery using the rubber band. A diagram of the electromagnet is shown. Describe the process of constructing an electromagnet and explain how it works.

• Wrap the wire around the nail and connect to the battery

• Place the nail on the battery

• Use the rubber band to hold the wire

• Connect the wire to the rubber band

The number of coils affects the strength of the electromagnet.

• Increases the strength

• Decreases the strength

• Has no effect

• Varies unpredictably

The teacher gives the student two bar magnets, as shown in the diagram. Which question is best answered by the electromagnet investigation?

• Why are the paper clips attracted to electromagnets?

• Which materials can be used to construct an electromagnet?

• What is the longest amount of time an electromagnet can function?

• How does the number of coils affect the strength of the electromagnet?

What can be concluded about the interaction between the magnets based on the observations?

• The magnets attract each other.

• The magnets repel each other.

• The magnets have no interaction.

• The magnets are broken.

Which statement best explains how the magnets interacted with each other even though they were separated by one centimeter of space?

• The magnets produced a field of force that extends beyond each magnet.

• The magnets produced a field of gravity that extends beyond each magnet.

• The magnets produced a field of electrical current that attracts and repels objects near them.

• The magnets produced a field of potential energy that attracts and repels objects near them.