# Measuring E & B Fields in Moving Frame

• whatsapro
In summary, the conversation discusses the measurements of E and B by an observer at rest and their values in a moving frame when another observer travels at a constant speed of v = .8c in the +x direction. It also explores the direction of F(em) according to both the observer at rest and the observer moving with a charge q = 1 micro C. The equations used are F(em) = q[E + v/c X B] and F'(em) = q[E' + v'/c X B']. There is confusion about which equation to use and the contribution of the E field to the force.
whatsapro

## Homework Statement

Suppose E and B are measured by an ovserver at rest to be (in N/C)
E = [0,0,60] B = [0,0,0]

Now another observer travels close by in the +x direction at a constant speed of v = .8c with respect to the other observer.

A. What is E' be in the moving frame? DONE
b. what will B' be in the moving frame? DONE
c. If a charge q = 1micro C travels with the moving observer (v = .8c in the +x direction), what is the direction of F(em) according to the observer at rest?

d. what is the direction of F(em) according ot the observer moving along witht he charge?

## Homework Equations

I assume F(em) = q[E + v/c X B] or the other ref frame version

## The Attempt at a Solution

Which one do I use? If the observer is at rest, wouldn't he be seeing the v = .8 c ? That would not even matter cause B = 0 anyways right? I would still use F(em) = q[E + v/c X B] right?

for part D. I would use F'(em) = q[E' + v'/c X B'] where v' = ? would it be 0 because they are traveling same v?

I understand that F(em) ne F'(em) but what is also confusing is that in both cases, the E field is the only contributing factor to the force. Is that assumption true?

Am I missing something here? Its copied exactly how it is written on paper.

## 1. How do you measure E and B fields in a moving frame?

To measure E and B fields in a moving frame, you would need to use special instruments such as a Faraday cage or an electromagnetic field meter. These instruments are designed to measure the strength and direction of electromagnetic fields. Additionally, you would need to take into account the motion of the frame and adjust your measurements accordingly.

## 2. Can E and B fields be measured in a vacuum?

Yes, E and B fields can be measured in a vacuum. In fact, electromagnetic fields are present in all regions of space, including vacuum. However, the strength of these fields may vary depending on the presence of other objects or sources of electromagnetic radiation.

## 3. What is the difference between E and B fields?

E and B fields are two components of an electromagnetic field. The E field, or electric field, is created by stationary charges and varies in strength and direction at different points in space. The B field, or magnetic field, is created by moving charges or changing electric fields and also varies in strength and direction at different points in space.

## 4. How does measuring E and B fields in a moving frame differ from measuring them in a stationary frame?

Measuring E and B fields in a moving frame requires taking into account the motion of the frame and adjusting the measurements accordingly. In a stationary frame, the E and B fields will remain constant, but in a moving frame, the fields may appear to change due to the motion of the frame.

## 5. What are some practical applications of measuring E and B fields in a moving frame?

Measuring E and B fields in a moving frame is important for understanding how electromagnetic fields behave in different situations, such as in a moving vehicle or near power lines. It is also crucial for designing and testing electronic devices and ensuring their proper functioning in various environments.

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