The electric motor

The Lorentz Force affects charged particles moving in a magnetic field, if the particles are crossing the magnetic field lines. A section of this wire passes through a magnetic field. The current is switched on. Now, charged particles are moving in the wire, crossing the magnetic field. They are affected by the Lorentz Force.

When the force affects the particles, they want to move. This makes the whole wire move. And if the current changes direction, the direction of the Lorentz Force is also changed. The wire moves in the other direction. Here, a loop of wire is placed in a magnetic field.

When the current is switched on, the charged particles cross the magnetic field lines here, and here. The Lorentz Force acts, this way … and this way. Confirm this with the right hand rule. The forces act in two different directions. This causes the loop to turn.

If the current changes direction, the Lorentz Force will act in the opposite direction. The loop turns again. Now it has rotated almost a complete turn. If the direction of the current keeps changing back and forth, the loop keeps rotating. It spins.

So, the current from the battery makes the loop rotate. Electrical energy in the battery is converted into kinetic energy in the loop. This is a simple electric motor. If we wind the wire many times to make it a coil, the Lorentz force becomes stronger and the rotation becomes faster. Now we have a high kinetic energy in the coil.

A strong electric motor that can turn the bit of a drilling machine … Or the wheels of an electric car. But how can we make the current change direction? It is direct current in a battery, and we can’t turn the battery all the time. Watch! The green and blue half circles are connected to the coil.

They are called segments. In the black part between the segments there can be no current. It is an insulator. The current runs from the blue segment, through the coil, to the green one. The coil spins.

Now, the green segment is on top. The segments have changed places. And now, the current runs from green to blue: in the opposite direction. The coil spins another half turn. The segments shift places, and now the current runs from blue to green again.

And so it goes on. The current changes direction all the time. The coil keeps turning. The Lorentz Force affects charges crossing a magnetic field. If a current runs through a coil inside a magnetic field, the coil is affected by the Lorentz Force.

The force can set the coil in motion and convert the electrical energy into kinetic energy. That’s how an electric motor works.