On the cabinet in my bathroom, a magnet holds the door closed. This means that one side (maybe the door) has a strong negative charge and the other side (maybe the cabinet itself) has a strong positive charge, so there is a force that pulls each toward each other. The hinge, however, creates a force that wants to force the two apart. If the electric force of the door magnet and cabinet magnet is not greater than the spring-like force of the hinge, then the door will not stay closed. The electric force of the two magnets can be calculated using the equation F = k(charge of door)(charge of cabinet)/the distance between the two ^2. This means that the force is constantly changing, increasing as the door swings more closed and decreasing as the door swings more open. The spring force of the hinge decreases as the door swings open, and increases as the door swings open. Unfortunately, we don't have any way to measure the charge of the door magnet and the charge of the magnet on the cabinet, so I don't have to do the calculation....
The door doesn't stay closed, as you can see in this picture, so the magnets are too weak for the electric force to overcome the force of the hinge. Cabinet = fail.... :P
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