Electromagnetism (Phys. 12)

In summary, an ion with a change of 1.6*10^-19 enters a 0.075 T magnetic field. If the ion follows a circular path of radius 0.083m, its momentum is 9.96*10^-22 kgm/s.
  • #1
Drevin
11
0
An ion with a change of 1.6*10^-19 enters a 0.075 T magnetic field. If the ion follows a circular path of radius 0.083m, what is the momentum of the ion?

I tried manipulating Fc = Fmagnet into Momentum = QBr, but that didn't work... any ideas?

Thanks!
 
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  • #2
What do you mean it didn't work?
 
  • #3
Doc Al said:
What do you mean it didn't work?
Well, it's a multiple choice question, and the answer I got wasn't any of them.
 
  • #4
Drevin said:
Well, it's a multiple choice question, and the answer I got wasn't any of them.

[tex]F = qvB[/tex]

You obviously know this. But what must the magnetic force do to keep the charge moving in a circle?
 
  • #5
Drevin said:
I tried manipulating Fc = Fmagnet into Momentum = QBr, but that didn't work... any ideas?
Write down the complete equation and the subsequent steps as you would have, for your homework. What you've written above is not an equation.
 
Last edited:
  • #6
Drevin said:
Well, it's a multiple choice question, and the answer I got wasn't any of them.
Your solution, "Momentum = QBr", is certainly correct. What were the other choices? If the choices were numerical, perhaps you made an arithmetic error.
 
  • #7
Doc Al said:
Your solution, "Momentum = QBr", is certainly correct. What were the other choices? If the choices were numerical, perhaps you made an arithmetic error.
The choices are:
A) 2.7 * 10^-26 kgm/s
B) 1.0 * 10^-21 kgm/s
C) 1.7 * 10^-12 kgm/s
D) 5.2 * 10^-4 kgm/s

The answer I got was 9.96 * 10^-22 using Momentum = QBR
mv = QBr
P = (1.6*10^-19)(0.075)(0.083)
P = 9.96 * 10^-22

That's what I did.
 
  • #8
Drevin said:
The choices are:
A) 2.7 * 10^-26 kgm/s
B) 1.0 * 10^-21 kgm/s
C) 1.7 * 10^-12 kgm/s
D) 5.2 * 10^-4 kgm/s

The answer I got was 9.96 * 10^-22 using Momentum = QBR
mv = QBr
P = (1.6*10^-19)(0.075)(0.083)
P = 9.96 * 10^-22

That's what I did.
Your answer is correct, except it is written to 3 sig figs, when it should only be written to 2. Do this, and you'll find that one the the given choices is correct.

I misunderstood what you'd written in the OP in my earlier post. After re-reading, it is clear what you did. My bad, sorry.
 
  • #9
significant figures

Drevin said:
The choices are:
A) 2.7 * 10^-26 kgm/s
B) 1.0 * 10^-21 kgm/s
C) 1.7 * 10^-12 kgm/s
D) 5.2 * 10^-4 kgm/s

The answer I got was 9.96 * 10^-22 using Momentum = QBR
mv = QBr
P = (1.6*10^-19)(0.075)(0.083)
P = 9.96 * 10^-22
You should realize that your answer is extremely close to one of those choices, so close that if you had to choose (and you do!) there should be no question as to which one to pick. (The other choices are off by many orders of magnitude--they aren't even close!) And, as Gokul says, if you had worked out your answer to 2 significant figures--as you should have, given the data--you would have found a perfect match. (Since the data you were given only had two significant figures, your answer must have no more than two significant figures.)
 
  • #10
Doc Al said:
You should realize that your answer is extremely close to one of those choices, so close that if you had to choose (and you do!) there should be no question as to which one to pick. (The other choices are off by many orders of magnitude--they aren't even close!) And, as Gokul says, if you had worked out your answer to 2 significant figures--as you should have, given the data--you would have found a perfect match. (Since the data you were given only had two significant figures, your answer must have no more than two significant figures.)
Ah, yes.. you're correct! (Our class doesn't tend to use sig figs very often, so I think that's where I got confused)

Thanks so much for the help!

I'll write down my steps a little more clearly next time I post a question, too.
 

What is electromagnetism?

Electromagnetism is a branch of physics that deals with the study of electromagnetic force, which is a fundamental force of nature. It is the force that allows charged particles (such as electrons and protons) to interact with each other and create magnetic fields.

How is electromagnetism related to electricity and magnetism?

Electricity and magnetism are two separate but interconnected phenomena that are described by the theory of electromagnetism. Moving electric charges create magnetic fields, and changing magnetic fields can induce electric currents. This relationship between electricity and magnetism is described by Maxwell's equations.

What are some real-world applications of electromagnetism?

Electromagnetism has numerous applications in our daily lives. Some examples include electrical generators and motors, which use the interaction between electricity and magnetism to produce energy; electromagnets, which are used in speakers, hard drives, and MRI machines; and wireless communication technologies, such as radio, television, and cellular networks.

What is the difference between an electromagnet and a permanent magnet?

An electromagnet is a temporary magnet that produces a magnetic field when an electric current passes through it. It can be turned on and off by controlling the flow of electricity. In contrast, a permanent magnet produces a constant magnetic field without the need for an external power source.

What is the electromagnetic spectrum?

The electromagnetic spectrum is the range of all possible wavelengths of electromagnetic radiation, from short gamma rays to long radio waves. It includes all forms of light, such as visible light, infrared radiation, ultraviolet radiation, and X-rays. Each type of radiation has different properties and uses in various fields, such as medicine, communication, and astronomy.

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