# Two Spheres connected by a wire.

1. Oct 12, 2009

### BustedBreaks

Charge is placed on two conducting spheres that are very far apart and connected by a long thin wire. The radius of the smaller sphere is 5 cm and that of the larger sphere is 12 cm. The electric field at the surface of the larger sphere is 830 kV/m. Find the surface charge density on each sphere

For the 12cm sphere I used this:

$$E=\frac{kQ}{R^{2}}$$

Solved for Q

Then divided by $$4\pi r^{2}$$, and got $$7.347 \frac{\mu C}{m^{2}}$$

I need a little help figuring out the charge density for the 5cm radius sphere.

2. Oct 12, 2009

### rl.bhat

When the two spheres are joined by a wire, their potentials are same.
So kQ1/R1 = kQ2/R2
Or (kQ1/R1^2)*R1 = kQ2/R2.
But E = (kQ1/R1^2) is given.
Find Q1 and Q2.