No electromobility without Lorentz force
It is now certain: the days of combustion engines are numbered and electromobility as a more environmentally friendly alternative is on everyone’s lips. It is a rapidly developing industry that aims to revolutionize the way we move. Unlike traditional vehicles that rely on combustion engines, electric vehicles use electric motors to drive their wheels. One of the basic forces required for the operation of electric cars, e-bikes or e-scooters is the Lorentz force. But how does an electric motor actually work and what role does the Lorentz force play? To understand this, we first need to go back to the late 19th century.
What is the Lorentz force?
The Lorentz force is a physical force that acts on a charged particle in an electromagnetic field, causing it to change direction. The magnitude of the force depends on the strength of the magnetic field B, the velocity of the particle v, and the charge q. Thus, the Lorentz force F is described by the formula F = q * v * B.
The discovery of the Lorentz force
Dutch physicist Hendrik Antoon Lorentz was working as a theoretical physicist at Leiden University, researching in the field of electrodynamics. He studied the interaction of electric and magnetic fields with charged particles, and discovered that a charged particle moving in a magnetic field is deflected by a force that is perpendicular to both the particle’s velocity and the magnetic field. In 1895, Lorentz described this force mathematically and later named it the “Lorentz force”. This discovery was an important milestone in the development of electrodynamics and remains of great significance today in many areas of physics and technology, such as particle acceleration, magnetic resonance imaging (MRI), and electromobility.
Nothing works without a magnetic field
In the field of e-mobility, the Lorentz force plays a crucial role in the operation of the electric motor. In electric cars, the motor typically consists of a stationary stator with copper wire windings and an inner, movable rotor. When the windings of the stator are supplied with three-phase current, an electromagnetic field rotates in the stator. A magnetic field is also generated in the rotor – depending on the type of motor, this can be through permanent magnets or a coil system. The interaction of both magnetic fields creates the Lorentz force, which causes the rotor to rotate and thus drives the vehicle forward.
What is the right-hand rule?
If the thumb points in the direction of the electric current and the index finger points in the direction of the magnetic field, the middle finger, bent at a 90-degree angle, indicates the direction of the Lorentz force.
Energy retrieval thanks to Lorentz force
The Lorentz force also plays an important role in the braking process of electric vehicles. In contrast to conventional brakes, which rely on friction, EVs typically use regenerative braking. When the car brakes, the electric motor system is used to convert the electric motor into a generator. The Lorentz force allows the retrieval of energy that normally escapes in the form of thermal energy during the braking process. The kinetic energy of the vehicle is thus converted into electrical energy and stored in the battery. This process is called recuperation. The use of Lorentz force for energy recovery has several advantages: Firstly, it can help increase the range of the vehicle. Secondly, it shortens the braking distance by making the EV more effective in coming to a stop. This also extends the life of the brakes, as they are less stressed.
The Lorentz Force in Student Experiments
As electromobility continues to grow, the Lorentz force will play an increasingly important role in everyday life. Therefore, this physical force is gaining importance in physics education as it is essential for understanding the functioning of electric motors. Conveniently, the Lorentz force can be effectively demonstrated and is therefore ideal as a student experiment. With our experiment kit ELECTRICITY 2 plus, students can discover the Lorentz force themselves and derive the three-finger rule in various experimental steps. In-depth experiments on the Lorentz force and its properties are possible with our experiment kit ELECTRICITY 4. In six different experiments, students can explore the vector property of the Lorentz force and the dependence of the Lorentz force on the magnetic field strength, current strength, length of the conductor, and the angle between the field and current strength.