Finding the Electric Field Needed to Suspend a Charged Bead

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Homework Help Overview

The problem involves determining the electric field strength required to suspend a charged plastic bead in air. The bead has a specified mass and a known excess of electrons, which contributes to its charge.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between force, electric field, and charge, referencing the equation F = Eq. There is an exploration of balancing forces acting on the bead, including gravitational force.

Discussion Status

Participants are actively engaging with the problem, suggesting various approaches to relate the forces involved. Some guidance has been offered regarding the need to consider gravitational force alongside the electrostatic force, but no consensus has been reached on the final calculations or values.

Contextual Notes

There is an emphasis on using the mass of the bead to find the gravitational force, which is necessary for further calculations. The discussion reflects uncertainty about how to integrate this information into the equations being used.

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1. Homework Statement
A 5.0×10^−2g plastic bead is charged by the addition of 1.0×10^10 excess electrons. What electric field (strength) will cause the bead to hang suspended in the air?


2. Homework Equations



3. The Attempt at a Solution
It has something to do with F = Eq but i don't know where to go about there
 
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Welcome to PF.

Let's see.

You figure F = E*q.

And if you draw a force diagram, what does E*q need to balance with?

They give you the mass ... hmm, what could you do with that?
 
So..

F=Eq

E=F/q - we know q but we need F.

For it to hang suspended, there needs to be no net force acting on the bead. The electrostatic force is one of two forces acting on the bead; as well as being the F in our equation. So...this "other force" needs to be equal to the electrostatic force.

Find the magnitude of this other force acting on the bead (the mass of the bead will come in handy...hint hint). As said, this force will be equal to the electrostatic force. Plug that into the above equation and solve for E. Good luck!
 
i'm assuming F= ma which leads to F = Mg but how does work into the equation

so mg = E*q

E = 4.9e-11 ?
 
Last edited:

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