Some electromagnetism questions

In summary, this question asks what the magnetic force is on an alpha particle moving in a direction perpendicular to a magnetic field. The correct answer is 5.3*10^{-14}N, but the alpha particle charge is 2e, not 4e.
  • #1
nunos
7
0
Can anyone please answer, and if possible, explain, this question? Thanks

1. A battery is connected between A and B of a bar made of semi-conductor of type P. The positive electrode was connected in A and the negative in B. What's the current direction?

A. from A to B
B. in the semiconductor it cannot pass any current
C. it depends on the type of the battery
D. it depends on the emf of the battery
E. from B to A
 
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  • #2
I'll give you a hint: The electric field goes from positive to negative potential. Now, what is the definition of current? Also, how does current flow in a semiconductor?
 
  • #3
That being said, I guess it's A.

Since it's being applied a corrent from the battery in point A, the positive pole of the semiconductor P, it will increase the potential there forcing some electrons to pass through.

If the semiconductor was of type N, the asnwer would be B, right?

I still have some confusion about this. The sole existence of a semiconductor of type P without the N-semiconductor it's kind of weird, since in most examples I have seen (not too many, though), they are almost coupled together...
 
  • #4
nunos said:
That being said, I guess it's A.

Since it's being applied a corrent from the battery in point A, the positive pole of the semiconductor P, it will increase the potential there forcing some electrons to pass through.

If the semiconductor was of type N, the asnwer would be B, right?

I still have some confusion about this. The sole existence of a semiconductor of type P without the N-semiconductor it's kind of weird, since in most examples I have seen (not too many, though), they are almost coupled together...

I'm not so sure about your statement about n-type semiconductors. It's been a while since I studied semiconductors, but doping a semiconductor, whether P or N-doping, should, if anything, increase its conductivity.

I believe the answer is A.
 
  • #5
Thanks espen 180 for your help. I can imagine how boring it might be for someone who is into physics to help a noob like me with such simple questions. I will keep this topic open if I have any more doubt.
 
  • #6
I can imagine how boring it might be...

Not at all. :) It's actually one of my main pasttimes.
 
  • #7
Another question:

An alpha particle is formed by 2 protons and 2 neutrons. If this one alpha particle moves with velocity 6.15e5 m/s in a direction perpendicular to a magnetic field |B| = 0.27T, what's the value of the magnetic force in the particle?

So I suppose the formula to use is the Lorentz Formula:

[tex]\stackrel{\rightarrow}{F} =q(\stackrel{\rightarrow}{E} + \stackrel{\rightarrow}{v} \times \stackrel{\rightarrow}{B})[/tex]

Since the electric field is non-existent and q = 4 times the mass of a proton

[tex]F = 6.69*10^{-27}*6.15*10^{5}\times 0.27 = 1.1*10^{-21}N[/tex]

Which is wrong, because the correct solution is [tex]5.3*10^{-14}N[/tex]

I suppose the problem is with the cross product... Any help is greatly appreciated. Thanks.
 
  • #8
Anyone?
 
  • #9
The charge of an alpha particle is 2e, not 4e. (Two protons and two neutrons.)
 
  • #10
nunos said:
q = 4 times the mass of a proton
This statement makes no sense, since charge and mass are different types of quantities. espen180 is correct.

In the future, please start a new thread to post a new question.
 
  • #11
I need some help with my physics ?'s?!
Can anyone help me?
 
  • #12
Please, people, you are welcome to ask questions at Physics Forums but you should really start a new thread with your question.

To start a new thread, go to the appropriate subforum and then click the "New Topic" button, near the top left of the page. It's the button that looks like this:

https://www.physicsforums.com/Prime/buttons/newthread.gif [Broken]​
[/URL]
 
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1. What is electromagnetism?

Electromagnetism is a branch of physics that deals with the study of the interactions between electrically charged particles and their surrounding electromagnetic fields.

2. How are electricity and magnetism related?

Electricity and magnetism are two different aspects of the same fundamental force, known as electromagnetism. They are related through the phenomenon of electromagnetism, where an electric current can generate a magnetic field and a changing magnetic field can induce an electric current.

3. What is an electromagnetic field?

An electromagnetic field is a physical field created by electrically charged particles that exerts a force on other electrically charged particles in its vicinity. It consists of both an electric field and a magnetic field, which are perpendicular to each other and together form an electromagnetic wave.

4. What are some real-world applications of electromagnetism?

Electromagnetism has numerous practical applications in our daily lives, including electricity generation, motors and generators, radio and television broadcasting, telecommunications, medical imaging, and many more. It is also the basis for technologies such as X-rays, microwaves, and lasers.

5. How does electromagnetism contribute to our understanding of the universe?

Electromagnetism plays a crucial role in our understanding of the universe, as it is one of the four fundamental forces of nature along with gravity, strong nuclear force, and weak nuclear force. It helps explain the behavior of matter and energy on both a microscopic and cosmic scale, from atoms and molecules to galaxies and the entire universe.

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