Finding the electric field between two parallel plates

Click For Summary
SUMMARY

The discussion revolves around calculating the electric field between two parallel plates given specific parameters of an electron, including its charge (-1.6 x 10-19 coulombs) and mass (9.11 x 10-31 kilograms). The participants highlight the necessity of knowing the length of the plates and the distance between them to solve the problem accurately. The kinematic formula and Newton's law are referenced, emphasizing the relationship between force, mass, acceleration, and electric field. The consensus is that additional geometric information is required to derive a definitive solution.

PREREQUISITES
  • Understanding of kinematic equations, specifically x = vot + 1/2 at2
  • Familiarity with Newton's laws of motion, particularly force = mass times acceleration
  • Knowledge of electric field calculations, specifically magnitude of electric field = force over charge
  • Basic understanding of particle physics, particularly properties of electrons
NEXT STEPS
  • Research the relationship between electric field strength and plate geometry in parallel plate capacitors
  • Study how to derive electric field equations from kinematic principles
  • Learn about the implications of varying distances between charged plates on electric field strength
  • Explore common mistakes in physics homework related to insufficient data and how to address them
USEFUL FOR

Students studying physics, particularly those tackling electromagnetism and kinematics, as well as educators seeking to understand common student challenges in problem-solving.

LuigiAM
Messages
55
Reaction score
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
 

Attachments

  • CEUQSBT.jpg
    CEUQSBT.jpg
    27.5 KB · Views: 1,173
  • nh5EqAt.jpg
    nh5EqAt.jpg
    42.5 KB · Views: 873
Physics news on Phys.org
I think you're right that you need more information about the plate geometry.
 
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.
 
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.
 
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?
 
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:
 
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:
 

Similar threads

  • · Replies 58 ·
2
Replies
58
Views
5K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 11 ·
Replies
11
Views
1K
Replies
4
Views
3K
Replies
11
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 10 ·
Replies
10
Views
5K
  • · Replies 6 ·
Replies
6
Views
1K
Replies
4
Views
2K