Finding the magnitude of electric field

AI Thread Summary
A uniform electric field exists between two oppositely charged parallel plates, with a proton released from the positively charged plate striking the opposite plate after 1.50×10−6 seconds. The user struggles to find the electric field's magnitude, initially using the wrong formula E=kQ/r², which is not applicable in this context. They express frustration over their understanding of the material and seek guidance on how to approach these problems effectively. Suggestions include focusing on the relationship between force, mass, and acceleration, and emphasizing the importance of understanding the underlying concepts rather than just memorizing equations. Persistence and seeking help from professors and teaching assistants are encouraged to improve comprehension in physics.
jlmccart03
Messages
175
Reaction score
9

Homework Statement


A uniform electric field exists in the region between two oppositely charged parallel plates 1.59 cmapart. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval 1.50×10−6 s .

Find the magnitude of the electric field.
Use 1.60×10−19 C for the magnitude of the charge on an electron and 1.67×10−27 kg for the mass of a proton.

Homework Equations


Coulomb: F = kQq/r2
F=ma
F=qE
E=kQ/r2
a=F/m

The Attempt at a Solution


First I have taken this course last spring and failed it. I simply do not understand how I set up these problems and get answers without being given an example. I literally bang my head against my desk and now I am doing the exact same thing just in a new semester. So I attempted to solve the problem this way.

I took E=kQ/r2 thinking that I could simly take the magnitude of Charge times Coloumbs constand divided by the distance squared. I get this E = 1.60*10-19 * 9*109 / 0.01592 to get 9*10-8 N/C. It's wrong. So I looked up a way to do this problem by Googling how to find electric field between two planes. I get E = V/d, but that is something we haven't learned yet so I think I am missing something and simply do not know where to go. How do you find electric field magnitude with the given equations? More so, how can I learn to tackle these problems since I just keep going one after the other not knowing what to do?

Thanks for any and all help given!
 
Physics news on Phys.org
jlmccart03 said:
E=kQ/r2
This is the electric field around a point charge, which is not relevant here.
jlmccart03 said:
How do you find electric field magnitude with the given equations?
You should first find the equation for the force on a charge. Once you have this, you can work out the needed variables from F=ma and the one-dimensional motion equations.
 
Last edited:
jlmccart03 said:
I literally bang my head against my desk
We've all been there...
jlmccart03 said:
More so, how can I learn to tackle these problems since I just keep going one after the other not knowing what to do?
There's no simple answer. My best advice is to try and understand the meaning of the formulas and their relation to reality as thoroughly as possible. Once you do that, it is just a matter of algebra. The biggest mistake you can make is to just try and memorize equations and hope they work.
 
NFuller said:
This is the electric field around a point charge, which is not relevant here.

You should first find the equation for the force on a charge. Once you have this, you can work out the needed variables from F=ma and the one-dimensional motion equations.
I managed to figure it out all on my own! And yeah I struggled last semester. I going to see my professor and TA's to see what I can do to make sure I understand the material. It's possible, I know I can do it, it just takes time and persistance to fight for an A in the class, but better an understading of how to do physics. Thanks!
 
jlmccart03 said:

Homework Statement


A uniform electric field exists in the region between two oppositely charged parallel plates 1.59 cmapart. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval 1.50×10−6 s .

Find the magnitude of the electric field.
Use 1.60×10−19 C for the magnitude of the charge on an electron and 1.67×10−27 kg for the mass of a proton.

Homework Equations


Coulomb: F = kQq/r2
F=ma
F=qE
E=kQ/r2
a=F/m

The Attempt at a Solution


First I have taken this course last spring and failed it. I simply do not understand how I set up these problems and get answers without being given an example. I literally bang my head against my desk and now I am doing the exact same thing just in a new semester. So I attempted to solve the problem this way.

I took E=kQ/r2 thinking that I could simly take the magnitude of Charge times Coloumbs constand divided by the distance squared. I get this E = 1.60*10-19 * 9*109 / 0.01592 to get 9*10-8 N/C. It's wrong. So I looked up a way to do this problem by Googling how to find electric field between two planes. I get E = V/d, but that is something we haven't learned yet so I think I am missing something and simply do not know where to go. How do you find electric field magnitude with the given equations? More so, how can I learn to tackle these problems since I just keep going one after the other not knowing what to do?

Thanks for any and all help given!
1499915841528.jpeg

I guess this will help.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Find the magnitude of the electric field at point P
Replies
5
Views
2K
What is the magnitude of the field at point R?
Replies
5
Views
2K
Find the Electric field at point p
Replies
2
Views
2K
Find the electric field between 2 finite discs
Replies
16
Views
1K
Magnitude of electric field E on a concentric spherical shell
Replies
17
Views
2K
Dependence of an electric field on distance
Replies
12
Views
2K
Coulomb's law to find electric field for charge density function
Replies
11
Views
1K
Confused about direction of electric field
Replies
7
Views
3K
What Is the Magnitude of the Electric Field Between Parallel Plates?
Replies
4
Views
2K
Understanding the energy of a dipole in a uniform electric field
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top