Want to make brushing your teeth even easier than it already is? Try using an electric toothbrush that uses an electric motor to rotate the brush back and forth to scrub your teeth better than ever. How does it work? On all the electric toothbrushes there is a battery at the bottom. This is used for a source of voltage which creates a current. As the current goes through the circuit, it reaches a point where it experiences a magnetic field. This creates a force upward on the circuit causing a net torque in the clockwise direction as shown in the diagram.
As the circuit rotates 180 degrees, the direction of the current switches; therefore, the direction of the force switches, so it turns around the rotation. This back and forth motion gets transferred to the brush which is why it is so effective in making teeth super clean and white.