Magnetic Field and electric Field

In summary: Well, if v were zero, then yes, but we are given that v is not zero. So, this vector equation is true if and only if the direction of B is exactly the opposite of v's direction. In other words, either v is zero, or B is in the opposite direction of v--i.e., parallel or antiparallel.In summary, when a charged particle with a constant velocity passes through a region with a zero external magnetic field, it is safe to conclude that the external electric field is also zero. However, when the external electric field is zero, it is not necessarily true that the external magnetic field is also zero.
  • #1
physicsdreams
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Homework Statement



A charged particle, passing through a certain region of space,has a velocity whose magnitude and directions remain constant.

a. If it is known that the external magnetic field is zeroseverywhere in this region, can you conclude that the external electric field is also zero? Explain.

b. If it is known that the external electric field is zero everywhere, can you conclude that the external magnetic field isalso zero? Explain.


The Attempt at a Solution



This is more of a conceptual question, and I really have no idea how to approach it.
If someone could help clarify this, that would be great!

Thanks
 
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  • #2
physicsdreams said:

Homework Statement



A charged particle, passing through a certain region of space,has a velocity whose magnitude and directions remain constant.

a. If it is known that the external magnetic field is zeroseverywhere in this region, can you conclude that the external electric field is also zero? Explain.

Well first of all I guess we have to assume that the particle doesn't experience any OTHER external forces, e.g. if it were confined to a wire or something. So from here on out I will assume the only forces possible are either electric or magnetic.

Suppose the electric field were nonzero. Then the charged particle would feel a force, and would thus experience some accelleration--i.e., its velocity's magnitude or direction would change.

b. If it is known that the external electric field is zero everywhere, can you conclude that the external magnetic field isalso zero? Explain.

This argument is slightly different. Remember the Lorentz force law : F = q(E+v x B). E is zero, so F = qv x B. Can this be zero for nonzero B?
 

FAQ: Magnetic Field and electric Field

1. What is a magnetic field?

A magnetic field is a region in space around a magnet or an electric current where the magnetic force is exerted on other magnets or moving charged particles.

2. How is a magnetic field created?

A magnetic field is created by the motion of electrically charged particles, such as electrons, within an object. This can occur naturally, such as in the Earth's core, or through the use of electricity, such as in electromagnets.

3. What is the difference between a magnetic field and an electric field?

A magnetic field is created by the motion of charged particles, while an electric field is created by electric charges. Additionally, a magnetic field exerts a force on moving charged particles, while an electric field exerts a force on stationary charged particles.

4. How are magnetic field and electric field related?

Magnetic fields and electric fields are closely related and can interact with each other. A changing electric field can create a magnetic field, and a changing magnetic field can create an electric field. This relationship is described by Maxwell's equations.

5. What are some practical applications of magnetic and electric fields?

Both magnetic and electric fields have a wide range of practical applications, including in motors, generators, speakers, and transformers. They are also used in medical imaging technologies, such as MRI machines, and in particle accelerators in scientific research.

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