# What Is the Force on a Charged Particle in a Magnetic Field?

• bdh2991
In summary: i ,
bdh2991

## Homework Statement

a particle with a charge of -1.24 x 10^-8 c is moving with instantaneous velocity v= 4.19 x 10^4 i + -3.85 x 10^4 j (both in m/s). what is the force exerted on this particle by a magnetic field a) 1.4 T i and b) 1.4 T k ?

## Homework Equations

F = qv x B (cross product not multiplication)

## The Attempt at a Solution

I tried using a determinate for part a where you put i j k and the velocity vector multiplied by q and then the magnetic field vector underneath that but i got -6.68 x 10^-4 i, however the books answers says that it is in the -k direction.

I don't understand the way my physics teacher does the cross multiplication that's why i tried using a determinate like in calculus...please help??

bdh2991 said:

## Homework Statement

a particle with a charge of -1.24 x 10^-8 c is moving with instantaneous velocity v= 4.19 x 10^4 i + -3.85 x 10^4 j (both in m/s). what is the force exerted on this particle by a magnetic field a) 1.4 T i and b) 1.4 T k ?

## Homework Equations

F = qv x B (cross product not multiplication)

## The Attempt at a Solution

I tried using a determinate for part a where you put i j k and the velocity vector multiplied by q and then the magnetic field vector underneath that but i got -6.68 x 10^-4 i, however the books answers says that it is in the -k direction.

I don't understand the way my physics teacher does the cross multiplication that's why i tried using a determinate like in calculus...please help??
Can you show your work ?

SammyS said:
Can you show your work ?

sure, this is what i was trying to do: for part a)

i , j , k
q(4.19x10^4) , q(-3.85x10^4) , 0
1.4 , 0 , 0

(i added commas in-between to not confuse)

i did the cross product using this determinate thinking it would give me the right answer and i got the right number just the wrong direction...

q(-3.85x10^4)(1.4) in the i direction, the book says -k direction...

bdh2991 said:
sure, this is what i was trying to do: for part a)

i , j , k
q(4.19x10^4) , q(-3.85x10^4) , 0
1.4 , 0 , 0

(i added commas in-between to not confuse)

i did the cross product using this determinate thinking it would give me the right answer and i got the right number just the wrong direction...

q(-3.85x10^4)(1.4) in the i direction, the book says -k direction...
Use the code icon, https://www.physicsforums.com/Nexus/editor/code.png , to display items with lots of spaces, like your determinant ... or simply use [CODE ] [/CODE ] tags.

Code:
i          ,                j            ,        k

q(4.19x10^4)  ,  q(-3.85x10^4)  ,    0

1.4           ,            0              ,     0

You are calculating your determinant incorrectly.

Show
what you multiply i by,
what you multiply j by,
what you multiply k by;​
including zeros, & prior to simplifying anything.

Last edited by a moderator:
I just figured out what i did wrong...i crossed out the columns and rows backwards...i didnt realize until you told me to write everything out lol thanks ...stupid mistake on my part

## What is a magnetic field?

A magnetic field is an invisible force that surrounds a magnetic object or is produced by an electric current. It is responsible for the attraction or repulsion of magnetic materials.

## How is a magnetic field created?

A magnetic field is created by moving electric charges, such as electrons, within a material. This can also be produced by an electric current, as the moving charges create a magnetic field around the conductor.

## What is the difference between magnetic field and magnetic force?

A magnetic field is the area around a magnet or electric current where other magnets or charged particles will experience a force. Magnetic force, on the other hand, is the actual force that is exerted on a magnet or charged particle by a magnetic field.

## How is the strength of a magnetic field measured?

The strength of a magnetic field is measured in units called Tesla (T) or Gauss (G). One Tesla is equal to 10,000 Gauss. The strength of a magnetic field is also influenced by the distance from the source of the field and the magnetic permeability of the material it is passing through.

## What are some real-life applications of magnetic fields and forces?

Magnetic fields and forces have many practical applications, including use in electric motors, generators, MRI machines, and compasses. They are also used in data storage devices, such as hard drives, and in particle accelerators.

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