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Bending Water and Turning Needles: Fields at a Science Fair

Grade 8 fields practice: analyze a charged comb bending a water stream and a current-carrying wire turning a compass to show forces act 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
11 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 use investigation data to show that electric and magnetic forces act across a gap.
Students describe how a field gets weaker with distance and how a wire's field depends on its current.
Students choose observations that rule out contact as the cause of a force.

How to use

If possible, show the comb and water stream demonstration first, then have students read the project notes and answer on their own.

Curriculum

NGSS standard covered

MS-PS2-5

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

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Name Date

Bending Water and Turning Needles: Fields at a Science Fair

Use two investigations to show that fields let objects push and pull without touching.

Investigation A: the comb and the water stream

Read the project notes and use Table A to answer the questions.

Science Fair Project Notes: Pushes and Pulls Across a Gap

1For the Harbor County science fair, eighth graders Kiri Tamatea and Bastian Mwangi wanted to know how objects can push or pull on each other without touching. Their teacher told them that scientists describe the space around a charged object as an electric field, and the space around a magnet or a wire carrying current as a magnetic field. Another object placed in a field can feel a force. The pair planned two investigations to find out whether they could detect these fields. Their display board asked two questions: can a force act across a gap, and if so, what makes that force stronger or weaker?

2Investigation A took place in Bastian's kitchen. They turned on the faucet so that a thin, smooth stream of water fell into the sink. Kiri ran a plastic comb through her dry hair 10 times and held the comb level with a mark 5 cm below the faucet, at a measured distance from the stream, never touching the water. A ruler taped behind the stream let Bastian measure on a photo how far the stream bent sideways. Kiri recharged the comb with 10 strokes before every trial, and the pair ran three trials at each distance and averaged them. With a comb that had not been run through hair, held 1 cm from the stream, the stream did not bend.

3Investigation B took place in the school lab. With their teacher's help, they laid a straight wire north to south directly over a compass, so that the wire and the needle pointed the same way. The wire was part of a circuit with a power supply, a switch, a small light bulb that keeps the current low and safe, and a meter that measures current in amperes (A). Their teacher set the power supply for each run. They recorded how many degrees the needle turned away from north. The wire sat 1 cm above the compass, except in one extra run at 2 cm. When the switch was open, the wire lay in the same spot but the needle pointed north. When they swapped the two wires on the power supply, the needle turned by the same amount in the opposite direction.