# Magnetic Field and the resulting force

In summary, when a moving charge (such as a magnet) interacts with a stationary charge, it loses energy in the form of heat.
Gold Member

## Homework Statement

This is not a homework Problem.Just a doubt.

The cross represents current-IN.
1-Magnetic field lines are produced in clockwise direction when current is going IN.
2-When wires carry currents IN,they form clockwise magnetic fields.So the magnetic fields of two wires join,forming a loop which attracts them(This is what my teacher said)
3-What happens in the case of a magnet?It won't form a "loop" because the field direction of the outer magnetic field of the magnet is opposite to that of the wire(A).But the inner field is in the same direction.

#### Attachments

• magnetic field lines.png
9.4 KB · Views: 549
That description from your teacher was a bit glib and incomplete. Hopefully you will study the forces on wire in an external magnetic field very soon.

A wire carrying a current does experience a force in the field of a magnet.
i.e. wire A will be deflected (roughly) upwards and to the right, wire B will be deflected upwards and to the left.

For two current carrying wires, consider the force on one current due to the field of the other wire: you'll see it follows the same rules.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/forwir2.html

1 person
Thank you so much.I have another question.
How was that rule and right hand thumb rule discovered?(I assume by an experiment)
Why does it always obey that rule?

The hand-rule is a kinesthetic mnemonic for remembering the relationship for a vector cross product.
Math is the language of physics, used to describe the relationships we discover in Nature - this particular relationship, which was discovered through many experiments, happens to be well described by a cross product.

Another question.
If a moving charge produce magnetic fields,will it lose energy?
Fr example,it attracts an iron nail and in that process the iron nail hits something and some of the energy becomes heat.
So the charge will slow down?

I haven't studied these in detail.Just the basics

The magnetic field is part of what a moving charge is so no.
An accelerating charge loses energy though - except in special circumstances.
Charges flowing in a wire can slow down as a result of the overall interaction.
How magnetic fields can be exploited to "do work" is subtle - see link at the bottom.

The nail - falling towards the magnet, exchanges EM potential energy for kinetic energy.
On impact, the kinetic energy is exchanged for elastic potential energy and heat.

http://van.physics.illinois.edu/qa/listing.php?id=17176 ... for better details.

1 person
Thanks.
I guess I will need to learn these things before thinking so much

## 1. What is a magnetic field?

A magnetic field is an area around a magnet or a current-carrying wire where a force can be exerted on another magnet or charged particle.

## 2. How is a magnetic field created?

A magnetic field is created by moving electric charges, such as electrons. This can occur naturally, as in the Earth's magnetic field, or artificially, through the use of magnets or electric currents.

## 3. What is the difference between a magnetic field and an electric field?

A magnetic field is created by moving electric charges, while an electric field is created by stationary electric charges. Additionally, a magnetic field exerts a force on other magnets or moving charged particles, while an electric field exerts a force on stationary charged particles.

## 4. How does a magnetic field affect the motion of a charged particle?

A charged particle moving through a magnetic field will experience a force perpendicular to both its direction of motion and the direction of the magnetic field. This force causes the particle to move in a curved path, known as a Lorentz force.

## 5. How can a magnetic field be used in everyday life?

Magnetic fields have a wide range of uses in everyday life, including in electrical motors, generators, and speakers. They are also used in MRI machines for medical imaging and in credit and debit card readers for data transfer.

Replies
7
Views
2K
Replies
8
Views
789
Replies
16
Views
775
Replies
2
Views
881
Replies
2
Views
498
Replies
14
Views
2K
Replies
1
Views
915
Replies
1
Views
1K
Replies
5
Views
522
Replies
37
Views
3K