From hospital MRIs to induction cooktops to kitchen cabinet doors, magnets and magnetism are everywhere. Indeed, if it were not for Earth’s magnetic field, life might never have evolved or survived. In this article, we show how simple & inexpensive magnet experiments can be used to demonstrate basic concepts.
North South Ferrite Bar Magnets
Magnets come in a variety of materials, strengths & prices. The Earth’s magnetic field, while very large, is also very weak. This makes ferrite bar magnets ideal for these experiments.
Ferrite bar magnets are inexpensive and safe for student use at home or school. They are just strong enough to pick up paper clips but not dangerous for little fingers. All our ferrite bar magnets use lead free paint. Just be to sure not to drop them on a hard surface since can chip or break. They are too weak to magnetize nails and other metal objects; best to buy an AlNiCo magnet for that.
How Many Paperclips Can a Ferrite Bar Magnet Lift?
Our first experiment was prompted by poor reviews we saw on a dominant on-line vendor’s site. Users complained they were so weak they couldn’t pick up even a couple of paper clips. (The product & its reviews disappeared the day after we first posted this blog several years ago.)
We put 40 paper clips into a 500ml beaker. A single 75x18x6.5mm ferrite bar magnet was dipped & swirled around inside the beaker to pick up as many paper clips as possible. The table below shows our bar magnet picked up an average of 22 uncoated steel paper clips.
|Paper Clip Type/Trial #||1st||2nd||3rd||4th||5th||Average # Picked Up|
|Plastic Coated Steel||13||11||13||9||9||11|
Ferrite Bar Magnet Repulsion Experiments
Two 75x18x6.5mm bar magnets were positioned so that like poles were opposite each other. The bars were then pressed together so they would repel each other. They were released & the distances they spread apart were measured. Results will vary depending on the smoothness of the underlying surface. A light coating of silicone or other oil may help reduce friction.
|1st||2nd||3rd||4th||5th||Average Distance Repulsed|
The video below shows our “test track” made out of Lego™ blocks to help constrain the bar magnets during repulsion. It also shows the bar magnets picking up the paper clips.
(Note: the videos feature our old domain name
www.indigo.com which we sold in 2018. You can buy magnets at www.indigoinstruments.com)
Another Way to Do Repulsion
Adding 20x10x5 neodymium rare earth block magnets to the ends of the 120mm long bar magnets greatly increased the repulsive force. We were able to achieve 150-200mm (6-8″) separation compared to less than 50mm (2″) without the boost.
Investigating Magnetic Fields with Ferrite Bar Magnets & Iron Filings
Our third experiment involves a petri dish, 1g of iron filings, a pair of 75mm bar magnets & a support stand made of molecular model parts. The support stand allows you to position the petri dish for hands free manipulating of the bar magnets to form patterns in the iron filings.