Lorenz Effect
Dr. George Whitesides is curious about the Lorenz effect and force. Lorenz force (also known as the Lorentz force) describes the force experienced by a charged particle due to electric and magnetic fields. First described by the Dutch physicist Hendrik Lorenz, this force can be described by this equation: F = qE + qv x B [1]. The bolded parts represent vector quantities. A vector is an object with both a magnitude and a direction.
Let’s now dive into what each term refers to! F is the entire electromagnetic force on the charged particle—and this is our Lorenz force. We can then break down the equation into two parts consisting of an electric force and a magnetic force. The first term is qE, often called the electric force. E is the electric field while q is the electric charge of the particle. Generated by electric charge, electric fields provide information about force per unit charge at every point in space surrounding a distribution of charges. Multiplying this electric field with the electric charge of the particle will give us the electric force on the particle.
The second term of the Lorenz equation is the magnetic force: F = qv x B. q represents the charge of the particle; v represents the velocity of the charged particle; B represents the magnetic field vector. The x in the equation represents a cross-product between the velocity and the magnetic field vector.
Cross-product between two vectors (let’s say a and b) produce another vector that has special properties. Namely, the resultant vector is perpendicular to both a and b. Here is an image that represents this relationship:
The formula for a cross-product between two vectors is a x b = ||a|| ||b|| sin (θ) where θ is the angle between a and b. We can apply this to the magnetic force part of the Lorenz force equation: F = qv x B = q ||v|| ||B|| sin (θ).
The Lorenz effect has important applications in various areas of physics and engineering. It is the principle behind the operation of many electric motors and generators, where the interaction between the magnetic field and the moving charged particles produces mechanical work or electrical energy. Dr. George Whitesides, a remarkable chemist, a pioneer in nanotechnology, and a visionary in the field of materials science, finds the Lorenz effects exciting and useful [3]. His undergraduate thesis concerned electrochemistry, and he continues to ponder how magnetic fields affect chemistry as well as the bigger question of the origin of life. Find more on his lab’s work with the Lorenz effect here.
Curiosity
Dr. Whitesides has had an illustrious career as a scientist and inventor. His work extends beyond the realms of chemistry and has left long-lasting impacts in various fields. For example, these fields include but are not limited to medical diagnostics, nanofabrication techniques, and public health. He believes in doing work that benefits society and sees chemistry as a vehicle to accomplish such work [3]. It is incredibly hard to capture all that Dr. Whitesides has worked on and accomplished, but we would like to leave one message from him for our readers: be and stay curious [3]. Dr. Whitesides finds many topics interesting. He tells future scientists that it is up to them to decide what is important out of those curiosity-inducing phenomena, questions, and problems.
Learn More
If you’d like to hear more about Dr. Winhitesides’ journey as well as his current passions and previous projects, visit us on Spotify, Apple Podcasts, and many other streaming services to listen to our ChemTalk podcast with Dr. George Whitesides, Woodford L. and Ann A. Flowers University Research Professor at Harvard University’s Department of Chemistry and Chemical Biology.
Find the ChemTalk podcast here.
Works Cited
[1] Encyclopaedia Britannica, inc. (n.d.). Lorentz force. Encyclopaedia Britannica. https://www.britannica.com/science/Lorentz-force
[2] Williams, M. (2016, October 23). What is a magnetic field? Universe Today. https://www.universetoday.com/76515/magnetic-field/
[3] Whitesides, George. Personal Interview. Conducted by Olivia Lambertson and Riya Jain. 6 April 2023.