Image charge: point charge and a sphere

This following applet is Image charge: point charge and a sphere
Created by prof Hwang Modified by Ahmed
Original project Image charge: point charge and a sphere

What happened when a charge Q is placed at a distance r from the center of an isolated metal sphere (net charge is zero) with radius R.
The following applet shows the field line distribution between charge Q and sphere.
You can drag the charge Q to different location and watch how the field distribution changed!

Red and green circle shown inside the metal are the image charge for this problem.
The electric field inside the metal is zero. All the electric field outside the sphere can be calculated frome elctric field due to charge charge Q and those two image charges.
Because net charge on the sphere is zero, so the sum of those two image charges is zero,too.
The image charge(green) at the center of the sphere is equal to Q*R/r;
The distance between red and green charge is R*R/r;

You can change the situation from isolated sphere to grounded sphere case.
Then, charge will flow to sphere to make the potential become zero.
The net charge will not be zero when the sphere is grounded.
The applet will show electric field, pontential contiur or charge distribution on the surface of the sphere if you click on those checkboxs.

If the charge Q is move inside the sphere, then one of the image charge(red) will be located outside the sphere.

You can study many related physics with this applet. I hope you can enjoy it as much as I do.

Embed a running copy of this simulation

Embed a running copy link(show simulation in a popuped window)

Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License

Please feel free to post your ideas about how to use the simulation for better teaching and learning.
Post questions to be asked to help students to think, to explore.
Upload worksheets as attached files to share with more users.

Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

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