Concepts Of Physics MCQ Edition [Volume 2]
- Exam
- Concepts Of Physics MCQ Edition [Volume 2]
- Subject
- Physics
- Chapter
- Magnetic Field
Concepts Of Physics MCQ Edition [Volume 2] · Physics · Magnetic Field
Suppose E and B represent the electric and magnetic fields in a...
Suppose and represent the electric and magnetic fields in a reference frame , while and represent them in another frame that moves with a velocity relative to . Which two of the following equations are incorrect?
Options
- A
- B
- C
- D
Correct answer
C.
Step-by-step solution
The Lorentz transformations for the transverse components of electric and magnetic fields in SI units, for a frame moving with velocity along the x-axis relative to , are given by:
B_y' = \gamma \left(B_y +\dfrac{v}{c^2}E_z\right)
where \dfrac{1}{\sqrt{1 - v^2/c^2}}.
For non-relativistic speeds (), , and the equations approximate to:
\dfrac{v}{c^2}
This can also be verified using dimensional analysis. In SI units, the dimensions of electric field and magnetic field are related by .
Thus, the term has the dimensions of an electric field, making equation (1) dimensionally correct.
Similarly, the term \dfrac{v E_z}{c^2} has the dimensions of \dfrac{[v][vB]}{[v^2]} = [, making equation (4) dimensionally correct.
Equations (2) and (3) are dimensionally inconsistent because \dfrac{v B_z}{c^2} does not have the dimensions of an electric field, and
B_y' = \gamma \left(B_y +\dfrac{v}{c^2}E_z\right)
where \dfrac{1}{\sqrt{1 - v^2/c^2}}.
For non-relativistic speeds (), , and the equations approximate to:
\dfrac{v}{c^2}
This can also be verified using dimensional analysis. In SI units, the dimensions of electric field and magnetic field are related by .
Thus, the term has the dimensions of an electric field, making equation (1) dimensionally correct.
Similarly, the term \dfrac{v E_z}{c^2} has the dimensions of \dfrac{[v][vB]}{[v^2]} = [, making equation (4) dimensionally correct.
Equations (2) and (3) are dimensionally inconsistent because \dfrac{v B_z}{c^2} does not have the dimensions of an electric field, and