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.

 

Ferrite Bar Magnets

Inexpensive ferrite bar magnets are suitable for attraction-repulsion and paperclip pickup. Do not to drop on to a hard surface such as concrete as they are quite brittle and will chip or crack. They do not require special storage or handling otherwise. Note that we only offer the 3 larger sizes on the right.

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
Uncoated Steel 19 18 21 28 22 22
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
46mm 44mm 43mm 42mm 44mm 44mm

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.

Single petri dishes are fragile & can break when shipped. Instead, we offer a 10 pack for classroom use or a single setup that comes with our electric circuits kit.

Petri dish with iron filings on a simple stand to allow hands free positioning of the bar magnets.

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