- #1
ILens
- 12
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Hi there!
I have a problem deriving the formula for the Lorenz force that I found in my lecture notes in Theoretical Mechanics.
The formula is:
[tex]\vec{F}=q \cdot \vec{E} + \frac{q \cdot (\vec{v} \times \vec{B})}{c}[/tex]
Where:
[tex]\vec{F}[/tex] is the Lorentz force
[tex]\vec{E}[/tex] is the electric field
[tex]\vec{v}[/tex] is the velocity of the charged particle
[tex]\vec{B}[/tex] is the magnetic field
[tex]q[/tex] is the charge of the particle
[tex]c[/tex] is the speed of light
The problem is that this relation is supposed to be formulated with respect to the "Meter, Kilogram, and Second" (MKS) measurement system (as stated in the lecture). According to the information I found, the expression for the magnetic field :
[tex]\frac{q \cdot (\vec{v} \times \vec{B})}{c}[/tex]
is written in terms of the "Centimeter, Gram, and Second" (CGS) measurement system ! It differs from the same expression in terms of the MKS system by the factor [tex]1/c[/tex] .
At the same time the expression for the electric field is in terms of the MKS system.
I have three problems:
1. I cannot understand whether the formulation of the Lorentz force, given in the lecture, is a correct one.
2. Is it possible to mix epressions written in terms of different measurement systems in one physical relation?
3. Where does the factor [tex]1/c[/tex], in the expression for the magnetic field in CGS, come from?
According to my calculation, this factor should be [tex]1/c^2[/tex] as it depends on the product of the permeability of free space and the permittivity of free space.
Permittivity of Free Space
If someone is able to help - thank you in advance!
ILens
I have a problem deriving the formula for the Lorenz force that I found in my lecture notes in Theoretical Mechanics.
The formula is:
[tex]\vec{F}=q \cdot \vec{E} + \frac{q \cdot (\vec{v} \times \vec{B})}{c}[/tex]
Where:
[tex]\vec{F}[/tex] is the Lorentz force
[tex]\vec{E}[/tex] is the electric field
[tex]\vec{v}[/tex] is the velocity of the charged particle
[tex]\vec{B}[/tex] is the magnetic field
[tex]q[/tex] is the charge of the particle
[tex]c[/tex] is the speed of light
The problem is that this relation is supposed to be formulated with respect to the "Meter, Kilogram, and Second" (MKS) measurement system (as stated in the lecture). According to the information I found, the expression for the magnetic field :
[tex]\frac{q \cdot (\vec{v} \times \vec{B})}{c}[/tex]
is written in terms of the "Centimeter, Gram, and Second" (CGS) measurement system ! It differs from the same expression in terms of the MKS system by the factor [tex]1/c[/tex] .
At the same time the expression for the electric field is in terms of the MKS system.
I have three problems:
1. I cannot understand whether the formulation of the Lorentz force, given in the lecture, is a correct one.
2. Is it possible to mix epressions written in terms of different measurement systems in one physical relation?
3. Where does the factor [tex]1/c[/tex], in the expression for the magnetic field in CGS, come from?
According to my calculation, this factor should be [tex]1/c^2[/tex] as it depends on the product of the permeability of free space and the permittivity of free space.
Permittivity of Free Space
If someone is able to help - thank you in advance!
ILens
Last edited: