A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the acceleration $\mathbf{a}$ different?
1. Yes
2. No
Note:
* Correct answer: B
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the particle velocity $\mathbf{u}$ different?
1. Yes
2. No
Note:
* Correct answer: A
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the magnetic field $\mathbf{B}$ different?
1. Yes
2. No
Note:
* Correct answer: A
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
Suppose we switch to frame with $\mathbf{v} = \mathbf{u}$, so that in the primed frame, $\mathbf{u}’ = 0$ (the particle is instantaneously at rest). Does the particle feel a force from an E-field in this frame?
1. Yes
2. No
3. depends on details
Note:
* Correct answer: A
## Announcements
* Extra credit assessment (Wednesday)
* Replaces second-lowest HW grade
* Last class (Friday)
* Wrap up and discussion
* Poster presentations (Monday, May 1 from 3-5pm in 1300 BPS)
* Hand out list of posters to review
* Hand out review sheets to complete
Minkowski suggested a better way to write $K^{\mu}$ is in terms of the field tensor, $F^{\mu\nu}$,
$$K^{\mu} = \dfrac{dp^{\mu}}{d\tau} = q\eta_{\nu}F^{\mu\nu}$$
What are the units of the components of the field tensor?
1. ${\frac{N}{m}}$
2. ${T}$
3. ${\frac{Ns}{Cm}}$
4. ${\frac{V}{m}}$
5. None or more than one of these
Note:
* Correct Answer: E (it's B and C)
<img src="./images/capacitor_S_Sbar.png" align="right" style="width: 600px";/>
Switch from frame $S$ to frame $\bar{S}$:
How does $E_x$ compare to $\bar{E}_x$?
1. $\bar{E}_x = E_x$
2. $\bar{E}_x > E_x$
3. $\bar{E}_x < E_x$
Note:
* Correct answer: A