Science
Strand IV
Use Scientific Knowledge from the Physical Sciences in Real-World Contexts

 

Science/Strand IV
Content Standard 3
All students will describe how things around us move and explain why things move as they do; demonstrate and explain how we control the motions of objects; and relate motion to energy and energy conversions. (Motion of Objects)

 

Science/Strand IV/Content Standard 3
Middle School

 

Science/Strand IV/Content Standard 3/Middle School
Benchmark 4
Use electric current to create magnetic fields and explain applications of this principle.

Benchmark Clarification

Electromagnets may be found in motors and generators. The Earth has a magnetic field at the North Pole and the South Pole. The location of the magnetic fields changes over time.

In an electromagnet, an electric current is applied through a conductive wire that creates a magnetic field around that wire.

A magnetic field is the area around a magnetic object where the force of the magnet can be detected. For example, if you take a wire, wrap it around an iron nail, and connect it to a battery it will result in a closed circuit. The electric current will create a magnetic field that will be able to pick up paper clips or other magnetic objects.

This same principle can be seen in junkyards (crane magnet) and doorbells. When a doorbell is pushed, a closed circuit results, causing the electromagnet to become magnetic; the armature (hammer that hits the bell) is then attracted to the electromagnet and hits the bell.

Students will:

  • Construct an electromagnet
  • Describe how an electromagnet works.

See Magnetic fields, (SCI.IV.1.MS.5).

Key Concept / Real World Context / Instructional Example / Assessment Example / Resources

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 4
Key Concept

  • electric current
  • magnetic poles
  • magnetic fields

Tools:

  • magnetic compass
  • battery
  • wire

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 4
Real World Context

  • electromagnets
  • bells
  • speakers
  • motors
  • magnetic switches
  • EarthÕs magnetic field

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 4
Instructional Example

Benchmark Question: How is electricity used to create a magnetic field?

Focus Question: Where is a magnetic field located in a simple circuit?

Small groups of students will place a navigational compass on a flat surface. They will pass a magnet near the compass, observe what happens, and discuss their observations.

Next, they will construct a simple circuit by using a 1.5 V battery and a twelve-inch length of bell wire (18-22 AWG insulated wire). Each student will write a prediction about where the magnetic field is located in the circuit. Then they will put a navigational compass flat on a desk or other flat surface. They will place the wire on top of the compass parallel to the needle and connect the battery to the ends of the wire. Each student will write observations of the movement of the compass needle. Students will compare and discuss results with the whole class.

After students have completed the activities, pairs of students will research and discuss one of the uses of electromagnets and the advantages and/or risks of those uses (MRI-magnetic resonance imaging, generators, etc.).

Note: When the circuit is connected, the battery gets hot and drains quickly. Limit connected time.

Constructing: (SCI.I.1.MS.1), (SCI.I.1.MS.5).

Reflecting: (SCI.II.1.MS.3), (SCI.II.1.MS.4).

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 4
Assessment Example

After students have completed an investigation on electromagnets and their construction, they will experiment with the effects of different variables on the strength of an electromagnet. Working in groups, students will design and conduct an investigation to test the strength of their electromagnet designs. Each student will write a hypothesis and predict how many paperclips the electromagnet can pick up. They may change the number of wire wraps, the length of wire, core size (nail thickness), change in current, and tightness and space of wire on the core. Each group should experiment with a different variable and construct a chart that shows how changes in that variable affect the strength of their electromagnet and the number of paperclips it is able to attract. Each student will write a lab report describing the investigation.

After sharing and discussing their results with the rest of the class, students should choose two of the variables and write an essay that discusses the following: the affect these variables have on the strength of the electromagnet, the number of wire wraps, the length of wire, the core size (nail thickness), the change in current, and the tightness and spacing of wire on the core.

See Electrical Connections.

(Give students rubric before activity.)

Scoring Rubric

Criteria

Apprentice

Basic

Meets

Exceeds

Correctness of ideas

Explanation contains few correct ideas.

Explanation contains some correct ideas.

Explanation contains many correct ideas.

Explanation contains all correct ideas.

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 4
Resources

Webliography.
http://mtn.merit.edu/mcf/SCI.IV.3.MS.4.html

Electrical Connections. AIMS.
http://wwws.aimsedu.org/aimscatalog/default.tpl

Electrical Units. STC. Carolina Biological Supply,1988.
http://www.carolina.com/

Machine Shop. AIMS.
http://wwws.aimsedu.org/aimscatalog/default.tpl

Magnetism and Electricity. Milliken, 1985.

Magnetism. TOPS.
http://www.topscience.com/

Mostly Magnets. AIMS.
http://wwws.aimsedu.org/aimscatalog/default.tpl