Magnetismum Physics Demo Lab 07/2013

Instructor Outline:

MagnetismUM Physics Demo Lab 07/2013

Lab length: 70minutes

Lab objective: To instruct the students aboutmagnetism, magnets, field lines, ferromagnetism, Earth’s magnetosphere, electromagnets and the Right Hand Rule for magnetic field, current and force.

NOTE: The students are to keep and label their electromagnets for Relay & Buzzer lab.

Materials

1 battery board

1 alligator lead card

1 bolt

1 spool of copper wire

2 ceramic Magnets

1 compass

1 fur strip

1 Petri dish of paper-clips

1 small “band steel” scraper(for removing wire enamel)

1 wooden block (compass pedestal, magnet pedestal and wire scraping backstop)

1 vector model set

8 Lorentz Force “swing sets”:

Cenco stand
bent wire “swing”
soda straw insulator
2 small binder clips for wire routing
2 small gauge clip leads (red and black)

Exploration stage: 35 minutes – Group Lab-Work

The students first explore the forces between the like and opposite poles of two ceramic magnets. They then assign north and south poles to the ceramic magnets using a compass. Next, the students detect the Earth’s magnetic field with a compass and assign the magnetic poles of the Earth to the geographic poles. They then bring a ceramic magnet and a bolt near the paper clips and observe the behavior of each. Students rub the bolt to see if that makes a difference in its magnetism, andfinally, they build an electromagnet and observe how current affects the strength of the electromagnet.

Analysis stage: 5 minutes –Lecture

The instructor analyzes with the class the findings in the exploration, and answers questions formed during that stage. Concept development is done on magnetism, field lines, ferromagnetism, electromagnets, and the equivalence of a current loop to a bar magnet.

Application stage: 30 minutes – Group Lab-Work

The students work in groups to observe and explore the behavior of magnetic forces on a current carrying wire using the Lorentz force “swing set”. They observe how the direction of the magnetic force depends on the relative orientation of the current direction and magnetic field and model the spatial relationship between force, current and magnetic field with three dimensional vectors. They are then shown how they can use their right hand to model the spatial relationships between current, field and force.

Concepts developed:

Magnets have two poles north and south, that cannot be separated.
Like magnetic poles repel, opposite magnetic poles attract.
The north geographic pole of the Earth is a magnetic south pole.
The magnetic field of the Earth points down as well as north at the latitude of Ann Arbor (dip needle demonstration).
Only moving charges (currents) produce a magnetic field and only moving charges experience magnetic forces.
Magnetic field lines indicate the direction and magnitude of the force on one magnet due to the presence of another magnet.
The direction of the force is tangent to the field line, attractive for opposite poles, repulsive for like poles.
The magnitude of the magnetic force is proportional to the local density of field lines.
The movement of a current-carrying wire depends on the direction of the current and the orientation of the magnet.

Suggested Demonstrations:

5H10.30 - Projection of the Fields of Permanent Magnets

5H15.40 - Projection of the Magnetic Field Due to a Current in a Solenoid

5H10.15 - Dip Needle

Introductory Lab Magnetic Force Balance apparatus

Introductory Lab Oersted Apparatus

Property of LS&A Physics Department Demonstration Lab