Finding the electric field between two parallel plates

In summary, the student is struggling with a homework problem and is looking for help from classmates.
  • #1
LuigiAM
55
7

Homework Statement



Hi everyone! This is the homework problem I'm struggling with!

CEUQSBT.jpg


Initial velocity = 107 meters per second
The particle is an electron, so:
Charge = -1.6 x 10-19 coulombs
Mass = 9.11 x 10-31 kilograms

Homework Equations



Kinematic formula x = vot + 1/2 at2
Newton's law: Force = mass times acceleration
Magnitude of electric field = force over charge

The Attempt at a Solution



I'm really at wit's end with this one guys :(

Basically, I've been trying to use kinematics from mechanics to solve this problem, but the way I've been doing it I haven't been able to get to the solution without knowing the length of the plates and the distance between them.

As you can see the professor gives us the answer to help guide us through the solution, but I just can't see how to get to it for this one problem.

My homework is for thursday so I have a lot more time to try and think of a solution, but I thought maybe you guys could maybe give me a tip about what step I may be missing.

This is the work I've done so far. I've assigned variables to represent the length of the plates and the distance between them. The only solution I was able to get was in terms of those variables. I assume there's a way to make them cancel out with something? Thanks for any help!

My work so far:

nh5EqAt.jpg
 

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  • #2
I think you're right that you need more information about the plate geometry.
 
  • #3
Clearly there is not enough information. If you make the horizontal distance greater, all the given data can stay the same but the field required would be less.
 
  • #4
Seriously? :frown:

Oh boy. I suspected that at first but I was sure that I was missing something. Should I write to the professor? He's over 80 years old so I don't want to offend him.
 
  • #5
LuigiAM said:
Seriously? :frown:

Oh boy. I suspected that at first but I was sure that I was missing something. Should I write to the professor? He's over 80 years old so I don't want to offend him.
Is it the prof's diagram? Quite sure there's no other data with it?
You could submit the answer you have... or do you have to submit it to a bot?
 
  • #6
LuigiAM said:

Homework Statement


Basically, I've been trying to use kinematics from mechanics to solve this problem, but the way I've been doing it I haven't been able to get to the solution without knowing the length of the plates and the distance between them.
Don't feel bad, I agree you need both h and d to obtain E.
So now someone else can prove us both wrong ... :smile:
 
  • #7
haruspex said:
Is it the prof's diagram? Quite sure there's no other data with it?
You could submit the answer you have... or do you have to submit it to a bot?

Yeah it's his diagram. There's nothing else, I just took a screenshot of the third question. We have to give it in class on paper

Last semester in mechanics he sometimes sent us emails to extend the date of a homework when he realized he had mistakes in them. I assume he might do the same again :sorry:
 

1. What is the formula for finding the electric field between two parallel plates?

The formula for calculating the electric field between two parallel plates is E = V/d, where E is the electric field, V is the potential difference between the plates, and d is the distance between the plates.

2. How do I determine the direction of the electric field between two parallel plates?

The direction of the electric field between two parallel plates is always perpendicular to the plates, pointing from the positively charged plate to the negatively charged plate.

3. Can the electric field between two parallel plates ever be zero?

Yes, the electric field between two parallel plates can be zero if the potential difference between the plates is also zero or if the plates are infinitely far apart.

4. How does the distance between the plates affect the electric field between them?

The electric field between two parallel plates is inversely proportional to the distance between them. As the distance increases, the electric field decreases and vice versa.

5. Are there any other factors that can affect the electric field between two parallel plates?

Yes, the electric field between two parallel plates can also be affected by the charge on the plates. The greater the charge, the stronger the electric field will be.

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