by Ron Kurtus

A total of 673 comments and questions have been sent in. They are listed according to date.

## List of next 10 letters

### Country

Electromagnetism What are photons? USA

Basics of Magnetism What is the repulsion equation of magnets? USA

Magnetism Magnetic lines of force and metals Thailand

Basics of Magnetism What is the basic concept of magnetism? India

Magnetism How to detect the direction of a magnetic field? Pakistan

Basics of Magnetism Calculate deflection of charge India

Moving Charges Create Magnetic Field Find intensity of electric field India

Basics of Magnetism Can you turn off a permanent magnet? USA

Moving Charges Create Magnetic Field When is AC used instead of DC? India

Magnetism Article on magnetism helped me USA

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First 10 letters

## What are photons?

Topic: Electromagnetism

### Question

November 18, 2014

Hello, reading this article helped understand electromagnetism a lot, but I am still left wondering on where and how photons ties into electromagnetism, if you can give me brief explanation it will be incredibly helpful to me to understand whatâ€™s being taught in my class.

- USA

25556

Electromagnetism ties in electricity and magnetism. However, then they oscillate, the combination of electrical and magnetic waves result in electromagnetic waves, such as light, radio, etc. See Overview of Electromagnetic Waves

In some situations, electromagnetic waves behave as particles called photons. This is part of what is called the wave-particle duality. Likewise electron particles can behave as waves.

## What is the repulsion equation of magnets?

Topic: Basics of Magnetism

### Question

September 30, 2014

My name is Jason. I am researching the repulsion of like poles on magnets, and my question: is there a formula that will determine the force of that repulsion or possibly any way to measure it?

- USA

25419

The equation for the force between two magnets is F = (mu)(q1)(q2)/4(pi)r^2, where (mu) is the permeability of the air, (q1) and (q2) are the magnitudes of the poles, (pi) = 3.14, and r is the separation.

A discussion and other equations can be seen at Force between magnets.

I hope that helps.

## Magnetic lines of force and metals

Topic: Magnetism

### Question

September 28, 2014

Through which material will magnetic lines of force pass the most readily?
Aluminum.
Copper.
Iron.

- Thailand

25408

Copper has the lowest permeability. Aluminum is next. The lines of force do not readily pass through iron.

## What is the basic concept of magnetism?

Topic: Basics of Magnetism

### Question

August 17, 2014

What is the basic concept of magnetism ?

Amit - India

25278

Magnetism is a force of attraction or repulsion that acts at a distance. It is due to a magnetic field, which is caused by moving electrically charged particles. It is also inherent in magnetic objects such as a magnet.

The basic concept is that moving electrical charges create a magnetic field.

## How to detect the direction of a magnetic field?

Topic: Magnetism

### Question

August 11, 2014

How the direction of magnetic lines of force is determined? who discovered that lines of force initiate from north pole and end at south pole and how? can the direction be determined without a compass?

naveed - Pakistan

25256

We know that there are lines of force between the north ans south poles of a magnet. It can be verified by sprinkling iron filings on a sheet of paper and putting a magnet underneath. You can also use a magnet to demonstrate the lines of force.

As far as the direction of the lines go, it is a convention agreed upon by ancient scientists, the same way as they agreed that an electric field goes from (+) to (-). There is no real way to detect which way the field goes.

## Calculate deflection of charge

Topic: Basics of Magnetism

### Question

July 10, 2014

I wanted to know the method to calculate the deflection of a charge when it enters a magnetic field with a velocity v.

Mousami - India

25104

The equation for the force on the charged particle is:

F = qvB, where F is the sideways force, q is the charge, v is the velocity, and B is the magnetic field strength.

## Find intensity of electric field

Topic: Moving Charges Create Magnetic Field

### Question

March 14, 2014

The intensity of electric field at a point 0.5m away from a point charge of 7.2 Nc . Find the magnitude of charge.

Mahender - India

24786

Electric field strength is force divided by charge: E = F/q.

In terms of distance: E = kQ/d^2, where k = 9*10^9 N-m/C^2 and d^2 = 0.25 m^2

Q is the source charge and q is the test charge.

I hope this helps.

## Can you turn off a permanent magnet?

Topic: Basics of Magnetism

### Question

March 8, 2014

I have a Question is possible to turn off a permanent magnet like a electric magnet

Gene - USA

24586

A permanent magnet is usually made of materials where the direction of the atoms is fairly fixed. The only way to "turn off" the magnetic field would be to heat the magnet to some high temperature, such that the atoms would be disorientated. Unfortunately, it is then difficult to re-magnetize the object.

## When is AC used instead of DC?

Topic: Moving Charges Create Magnetic Field

### Question

January 25, 2014

I am not understanding condition when AC source use in place of dc source.

vishnu - India

24464

In DC electricity, the electrons move directly through the wire. In AC, the electrons alternate back and forth.

In many devices, such as a light bulb, it does not matter whether AC or DC electricity is used. However, there are DC electric motors that only work with DC electricity. Also, some electrical circuits require AC and will not work with DC.

## Article on magnetism helped me

Topic: Magnetism

### Question

January 14, 2014

I wanted to e-mail you and say thanks for putting together your web site's Basics of Magnetism page: www.school-for-champions.com/science/magnetism.htm ...The page has some useful information and resources and I found it to be helpful while creating my article on magnetic fields: www.magnatag.com/page/ARTICLE-2014-01-09-9/article.asp

Thomas - USA

24433

Thanks for the feedback. I'm glad the material was useful to you. Best wishes in your work.

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