The Effect of Electric Forces on Water Now let's do the same thing with a water molecule. We'll be using electric forces instead of magnetic forces, so we have to replace the magnet with an electric charge. And that thing that looks like a mouse head is the water? Yep. That thing represents one molecule of water -- good old H2O. The big atom is oxygen and the two little attached ones are hydrogen. Click and drag on the negative charge to move it. The water molecule rotates in the same way that the compass needle did. But why does it rotate? There are electric forces acting on the water molecule that cause it to rotate when the negative charge is brought near it. Does the water molecule have electric charges on it? Yes, a water molecule has a positively and a negatively charged side (just like the compass needle has a north and a south pole). We know that like charges repel and unlike charges attract, so when the negative charge is brought near the water molecule, there are electric forces acting on both ends. If the forces are like this, it's just like a steering wheel on a car. One side pushes, the other side pulls, and so the wheel rotates. 6th