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Feedback Comments on Magnetism

by Ron Kurtus

A total of 674 comments and questions have been sent in. They are listed according to date.

You can read them to further your understanding of the subject.

List of most recent 10 letters




Magnetic Materials Wands free books on EMF Ethiopia
Moving Charges Create Magnetic Field How is magnetic field created? India
General Device using small disc magnet Canada
Solenoids Solenoid and electromagnet India
Basics of Magnetism Questions on electromagetism India
Electromagnetic Devices How do electromagnets work in railway signals? India
Electromagnets Placing electromagnet inside another electromagnet USA
Magnetic Materials Srength of neodymium super magnets Philippines
Electromagnetism Why is copper used in a motor's stators? USA
Magnetism Lorentz Applying Lorentz force at the equator India

Next 10


Wands free books on EMF

Topic: Magnetic Materials


May 30, 2018

Hello I am bereket, age 20 and I'm from Ethiopia. I want to ask you how I can get free online books on EMF.

Bereket - Ethiopia



There are some free downloads on EMF from Free Books - EMF.

I'm not sure how extensive they are, but they might give you what you want.

Best wishes for success in your studies.

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How is magnetic field created?

Topic: Moving Charges Create Magnetic Field


November 7, 2017

how megnetic field created around electric current

ravi - India



Electrical charges have an electric field around them. When the charges move a magnetic field is created perpendicular to that movement. An electric current consists of moving electrical charges.

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Device using small disc magnet

Topic: General


September 6, 2017

Good morning Ron. My son and I are developing a low tech medical device that relies on the attraction between a small disc magnet 20 mm x 2 mm and a similarly sized flat washer. We're having a problem with the amount of attraction between the two and need to increase it and are thinking about increasing the size of the magnet or the washer but are constrained in doing this due to physical dimensions. Is there anything readily available such as a flat washer or disc with a higher than normal iron content that would cause the magnet to be more strongly attracted to it? Many thanks!

Niall - Canada



You might try a Neodymium disc magnet. They are small, strong and inexpensive and can be bouht through or other outlets.

I hope that helps. Best wishes for success with your device.

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Solenoid and electromagnet

Topic: Solenoids


June 13, 2017

Why solenoid is used for making electromagnet

Nishant - India



A solenoid is an electromagnet without the iron core in it. The solenoid can be used to pull a core inside it.

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Questions on electromagetism

Topic: Basics of Magnetism


February 17, 2017

DC Electromagnet.
1. Ratio of Core area & Poles face area.
3. If three sides of magnet is covered with non magnetic material will there be more force on pole faces.
4. Construction & operation details of

tks. rgds, Vish

Viswanatan - India



See our lessons on Electromagnetism. They should help answer some of your questions.

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How do electromagnets work in railway signals?

Topic: Electromagnetic Devices


February 14, 2017

How electromagnet works in railway signals?

Harsh - India



Railway signals can be flashing lights or a moving barrier.

An electromagnet could be used as a solenoid to turn on or turn off the railway signals.

The barrier is usually moved by an electric motor.

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Placing electromagnet inside another electromagnet

Topic: Electromagnets


February 5, 2017

I have a new found curiosity for electromagnets. I'm not a scientist or even a student... just curious. What would happen if your electromagnet core contained another electromagnet?

Ron - USA



If the core is movable, you would have a solenoid of sorts. (See Solenoids are Electromagnetic Devices).

Instead of having a movable iron core or magnet core, you would place an electromagnet there. This would allow movement of the core to be finely tuned. However, I don't think I've even seen such a configuration.

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Srength of neodymium super magnets

Topic: Magnetic Materials


April 15, 2016

I have 3 pcs N52 neodymium super magnets. How do I know the strength of attraction between the two of them in contact with each other without anything in between, or conversely how strong they will push each other apart it they measure 10 mm x 5 mm x 2 mm, with the poles on the larger faces (5 x 10) and, if the poles are on the smaller faces (5 x 2)?

Junnel - Philippines



Since there is a wide variation on the strength of neodymium super magnets, the best way to find the strength of attraction and repulsion would be to experimentally measure it. For example, you could use a spring scale to measure the force required to pull the two magnets apart.

Other than that, I don't readily know of equations to allow you to predict the forces.

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Why is copper used in a motor's stators?

Topic: Electromagnetism


April 5, 2016

Hi Ron,

My question, if you don't mind, is why do I see copper used if iron in the below stator if they are weak magnets? Cost?

Thanks for the information on your site and for replying to me email if you have the time.

Richard - USA



The stator in an electric motor is the stationary part of the motor’s electromagnetic circuit. It usually consists of copper windings to create the magnetic field.

The copper is much more efficient than using iron wire.

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Applying Lorentz force at the equator

Topic: Magnetism Lorentz


March 2, 2016

is there is a possibility for applying the lorentz force in the earth magnetic field at the equator?

- India



The Lorentz force has been use with wires having from a space vehicle in order to create a current from the Earth's magnetic field.

However, the movement of a wire at the equator would not be enough to create a current.

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