# Investigating Interactions Between Electric and Magnetic Fields

## A Carolina Essentials™ Activity

##### Total Time: 60-75 min

Prep: 30 | Activities: 30-45ea

## Introduction

A foundational concept in physics is the relationship between electricity and magnetism. Common devices such as electric motors and generators apply the relationship between electric and magnetic fields.  The two forces producing the fields are so intertwined that we usually refer to the relationship as electromagnetism.  This activity is a simple and visual way for students to investigate the relationship between electrical conductors producing electric fields and magnetic fields.  By taking time data for neodymium magnets falling through copper, aluminum, and PVC pipes, students identify variables contributing to the existence, strength, and interactions of electric and magnetic forces.

### Phenomenon

As a demonstration, set up identical lengths of three types of pipes: copper, aluminum foil tube, and PVC, and simultaneously drop a metal nut from the top of each pipe. All three nuts should fall at the same velocity and hit the bottom at the same time. This demonstration helps students focus on the relationship between the magnetic field and the material from which the pipe is made.

## Activity Objectives

1. Conduct an investigation to gather data for a magnet interacting with 3 different materials.
2. Use data to explain the interaction of magnetic and electric fields.

## Next Generation Science Standards* (NGSS)

PE: MS-PS2-5. Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.

### Science & Engineering Practices

Planning and Carrying Out Investigations

### Disciplinary Core Ideas

PS2.B: Types of Interactions

Cause and Effect

## Teacher Preparation and Disposal

Purchase the pipe materials and precut the pipes into lengths that match the lengths of the aluminum foil tubes. Lightly sand the ends of the pipes to remove any burrs.  Secure the pipes and aluminum foil tube with a clamp to a ring stand for more precise timing.  The bottom edge of the pipes and tube should be 15-20cm above the desk to facilitate timing.  Cushion the fall of the magnets as they hit the desktop with folded up towels, several folded paper towels, bubble wrap, or foam packing material placed directly under the pipes and tube.  Neodymium magnets chip easily.  All materials can be reused.

## Safety

The neodymium magnets are strong.  Keep your fingers and hands from between the magnet and other magnetically attractive bodies.  Do NOT put magnets in your mouth.

## Procedure

### Student

1. Place a pipe in the clamp attached to the support stand. The bottom edge of the pipe or tube should be 15-20cm above the base of the support stand.
2. Add a cushion made from a folded towel, paper towels, bubble wrap, or foam packing material directly under the pipe or tube.
3. Place one magnet at the top edge of the pipe or tube.
4. Drop the magnet down the center of the tube.
5. Measure the time, in seconds, it takes for the magnet to fall the length of the tube.
6. Repeat the procedure for a total of 5 trials.
7. Experiment with additional numbers of magnets, recording the number of magnets used and the time in seconds.
8. Complete the same procedure for the other two pipes.
9. Your teacher may make a class data table to record all group data.
10.

### Teacher

Phenomenon Procedure:  Set up all three pipes, secured in support stands, with a cushion under the pipes and tube to catch the nut. Release a nut down the center of the pipes and tube at the same time.   Have students write down their observation.  You may need to repeat the procedure several times. All nuts should fall at the same rate.  No force interactions.

To reduce time, you may want to set up stations-one type of pipe per station and instruct student to rotate through the three stations. If materials allow, students can also work in a lab group of 3.

Make certain that the pipes are measured correctly, using the aluminum foil tube as a standard.

You may want to set up a class data table to increase the number of trials. Ask students to average the data.

## Data and Observations

Construct a data table for 5 trails on each of the 3 types of pipe or tube.  Student data will vary slightly.

#### Data Part 1: Time for 1 magnet to fall (s)

Trial Aluminum Copper PVC
1
2
3
4
5

## Analysis: Part 1

1. Average the total time for the magnet to fall over the 5 trials for each type of pipe.
Students answers will vary but all groups should have similar data.

## Discussion

1. Which type of pipe or tube interacted most strongly with the magnet? What evidence supports your claim?

Electric conductivity (10.E6 Siemens/m)

• Silver 62.1
• Copper 58.7
• Gold 44.2
• Aluminum 36.9

https://www.tibtech.com/conductivite.php?lang=en_US

Copper slowed the magnet the most, so it produced the strongest electrical field to interact with the magnetic field. See the electrical conductivity table above.

2. Which type of pipe or tube interacted the least with the magnet? What evidence supports your claim? PVC – had no effect on the time it took the magnet to fall.

3. Explain which pipes or tube are most likely electrical conductors. What evidence supports your claim? Copper and aluminum are electrical conductors. Both pipes increased the time for the magnet to fall. See the table above.

4. Explain whether the number of magnets made a difference in the time. More magnets create a stronger magnetic field strengthening the opposing interacting forces, increasing the time it took the magnet to fall.

5. Using your data as evidence, explain the interaction between electric and magnetic forces. There are opposing forces, the magnetic field and the electric field, interacting between the magnet and the copper and aluminum pipes which increases the time it takes for the magnet to fall. This is Lenz’s Law.

6. Using the same materials, how could this experiment be modified to collect additional data to support the claim you made in item 4. Student answers will vary but here are some suggestions. Take some aluminum off the roll to investigate if the time changes. Use a ring magnet traveling on the outside of the pipe instead of the disk magnet traveling on the inside of the pipe. Lengthen the pipes.