Calculate mass of oil droplet between parallel plates

AI Thread Summary
To calculate the mass of an oil droplet held motionless between parallel plates with a potential difference of 39.8 kV, the electric force acting on the droplet must be equal to its weight. The droplet carries an extra charge of one electron, which allows for the calculation of the electric force using the potential difference. The gravitational force can be expressed as the weight of the droplet, leading to the equation that equates the two forces. The solution involves finding the electric force and using it to determine the mass of the droplet. This approach simplifies the problem significantly.
PhysicsMan999
Messages
32
Reaction score
0

Homework Statement



  1. A droplet of oil, carrying an extra charge of one electron, is held motionless between parallel plates separated by 1.89 cm, with a potential difference of 39.8 kV. What is the mass of the droplet?

2. Homework Equations

E=0.5QV
C=Q/V

The Attempt at a Solution


Really don't even know how to start here..I figured I would need kinetic energy to find the mass but the velocity is 0, so there would be none.[/B]
 
Physics news on Phys.org
PhysicsMan999 said:

Homework Statement



  1. A droplet of oil, carrying an extra charge of one electron, is held motionless between parallel plates separated by 1.89 cm, with a potential difference of 39.8 kV. What is the mass of the droplet?

2. Homework Equations

E=0.5QV
C=Q/V

The Attempt at a Solution


Really don't even know how to start here..I figured I would need kinetic energy to find the mass but the velocity is 0, so there would be none.[/B]

The problem should really tell you this, but you should assume that the force holding the droplet fixed is the weight of the droplet. Find the electric force on the droplet and set it equal to the gravitational force.
 
Oh, well that was easy then. Thanks!
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Back
Top