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Studio Speakers: Measuring a Magnetic Field

Grade 8 fields practice: analyze phone magnetometer readings near a speaker magnet, test materials in the field and explain forces without contact.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS2-5

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
10 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Matching, Sorting, Short answer

About this worksheet

What students practice

Students analyze magnetometer data to describe how a magnetic field changes with distance.
Students evaluate an investigation that tests whether a magnetic field passes through materials.
Students use evidence to explain that fields let objects exert forces without touching.

How to use

Read the studio notes together, then have students answer from the tables. If phones with a free magnetometer app are available, groups can repeat the distance test with a fridge magnet.

Curriculum

NGSS standard covered

MS-PS2-5

Investigate how fields let objects exert electric and magnetic forces on each other without touching.

Preview

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Name Date

Studio Speakers: Measuring a Magnetic Field

Investigate forces that act across space in a recording studio.

The field and distance

Read Lucía's studio notes and study Table 1. Then answer the questions.

Why Phones Stay Off the Speakers

Lucía Marangoni spent a week of her summer break shadowing sound engineer Caspian Adeyemi at a small recording studio. The studio's large speakers, called monitors, each hold a strong permanent magnet. When music plays, an electric current in a coil of wire near the magnet makes the coil push and pull, and the coil moves the speaker cone that makes the sound. Caspian asks musicians not to rest their phones on the monitors, because a strong magnet close by can make the compass in a phone point the wrong way.

Lucía wanted to know how far the magnet's effect reaches. Caspian gave her the magnet from a broken speaker and a phone app that reads the phone's magnetic sensor in microteslas (µT). She set the magnet on a wooden table and laid a meter stick beside it. First she took a reading with the magnet far away. That reading came from Earth's own magnetic field, so she subtracted it from every later reading. Then she moved the phone along the meter stick, took three readings at each distance and averaged them. She kept the phone flat and facing the same way for every reading, and she moved her keys and other metal objects off the table first. Table 1 shows her results.

Next, Lucía held the phone 15 cm from the magnet and slid a flat sheet of material into the space between them, without letting it touch either one. She tested a piece of cardboard, a wooden cutting board, a few layers of aluminum foil, a plastic tray and a steel baking sheet. Table 2 shows her readings.

Lucía also laid a sheet of paper over the magnet and sprinkled iron filings on the paper from a shaker. The filings never touched the magnet, yet they lined up in curved lines that ran from one end of the magnet to the other. The lines crowded close together near the two ends and spread out farther away.

Later, Caspian pulled a vinyl record out of its paper sleeve. A loose strand of Lucía's hair lifted toward the record from several centimeters away, and specks of dust jumped onto its surface.