# What Are the Correct Equations for Solving Magnetism Problems?

• shikagami
In summary, the first solution uses the equation V=(kq)/r and the second solution uses the volts equation: V=PE/q.
shikagami
I'm confused if I am using the right equations to solve this problem.

P: A singly charged Li^7 ion has a mass of 1.16x10^-26kg. It is accelerated through a potential difference of 500 Volts and then enters a magnetic field of 0.4 Teslas, moving perpendicular to the field. What is the radius of its path in the magnetic field.

I had two different solutions to this problem that has to completely different answers. First, I figured I can use the equation V=(kq)/r. Then I solved for the radius. The second way is by using the volts equation: V=PE/q, which I use to solve for the potential energy. I then used this in the kinetic energy equation KE=1/2mv^2 to solve for the velocity. This velocity I then used in the equation r=(mV)/(Bq). I got 2.88x10^-12 meters for the first solution and 3.44x10^13 meters for the second solution. Which one is right is any?

What is your understanding of V=(kq)/r? How did you use it?

Well... since I knew how much volts there is, I figured that it is faster to just use that formula where k is the Coulomb constant (8.99x10^9 Nm^2/C^2), then just solve for the radius. Is it possible to use this equation like that?

shikagami said:
Well... since I knew how much volts there is, I figured that it is faster to just use that formula where k is the Coulomb constant (8.99x10^9 Nm^2/C^2), then just solve for the radius. Is it possible to use this equation like that?

No. The r in that equation is distance from a charge q and the V is is the electric potential due to that charge. It has nothing to do with the radius of curvature of a path of a particle, and that V is for a completely dirrerent geometry than what you have.

So is my second solution the right one? or are they both wrong?

## 1. What is magnetism and how does it work?

Magnetism is a fundamental force of nature that is responsible for the attraction or repulsion between objects. It is caused by the alignment of electrons in certain materials, creating a magnetic field. This field can interact with other magnetic fields, causing objects to either attract or repel each other.

## 2. What are some real-life applications of magnetism?

Magnetism has a wide range of applications in our daily lives. It is used in motors, generators, speakers, and hard drives. It is also important in the fields of medicine, transportation, and energy production.

## 3. What factors affect the strength of a magnetic field?

The strength of a magnetic field depends on the material, the shape and size of the magnet, and the distance from the magnet. The strength is also affected by the presence of other magnetic fields in the surrounding environment.

## 4. How can we manipulate or control magnetism?

Magnetism can be manipulated or controlled by using different materials, changing the shape and size of the magnet, and varying the distance between magnets. Additionally, electromagnets can be used to produce a magnetic field that can be turned on or off.

## 5. How does magnetism relate to electricity?

Magnetism and electricity are closely related, as they are both forms of electromagnetic energy. Moving electric charges create a magnetic field, and a changing magnetic field can induce an electric current. This relationship is known as electromagnetism and is the basis for many technological devices.

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