Potential difference between the plates?

AI Thread Summary
A charged object suspended between the plates of a parallel-plate capacitor requires calculating the potential difference. The initial calculation yielded an incorrect value of 5.561 kV. The correct approach involved resolving the forces acting on the object, using Tcos(theta) for gravitational force and Tsin(theta) for electrostatic force. The electric field was then calculated as E = F/q, leading to the final potential difference of 1.387 kV. This method successfully determined the potential difference between the plates.
dark_angeL23
Messages
2
Reaction score
0

Homework Statement



A small electrically charged object is suspended by a thread between the vertical plates of a parallel-plate capacitor. The acceleration of gravity is 9.8 m/s^2.
What is the potential difference between the plates? Answer in units of kV.

Given: tetha = 14 degrees
mass of the object = 152 mg
q = 15 nC
distance between the two plates = 5.6 cm


Homework Equations



I used the following:

delta V = U/Q
U = F x d


The Attempt at a Solution




I got U = 0.0000834176 Joules
and I got V = 5561.1733333 V
which is V = 5.561173333 kV

but it's wrong.

could someone please please tell me how to do it?
 
Physics news on Phys.org
dark_angeL23 said:

Homework Statement



A small electrically charged object is suspended by a thread between the vertical plates of a parallel-plate capacitor. The acceleration of gravity is 9.8 m/s^2.
What is the potential difference between the plates? Answer in units of kV.

Given: tetha = 14 degrees
mass of the object = 152 mg
q = 15 nC
distance between the two plates = 5.6 cmI got U = 0.0000834176 Joules
and I got V = 5561.1733333 V
which is V = 5.561173333 kV

but it's wrong.
could someone please please tell me how to do it?

Welcome to PF.

How did you resolve the force of gravity and the electrostatic force to determine your E field?
 
Thank you.

I got it.
It took forever to finally get a reply from someone, so I asked someone else.

What I did was Tcos(tetha) = (152x10^-6)(9.8)
then, F=Tsin(tetha)

Then I used, E=F/q
Then I used, V=Ed, V/1000 (conversion from V to kV)

My final answer is V = 1.386556241 kV

And it's correct! :smile:
 
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...
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}...
Back
Top