Explore the invisible forces that guide charged particles and create the foundation of electromagnetism.
A charged particle moving through a magnetic field experiences a force perpendicular to both its velocity and the magnetic field direction. This fundamental force is responsible for everything from the aurora borealis to the operation of electric motors.
The cross product means the force is always perpendicular to the plane containing velocity and magnetic field. This causes charged particles to move in circular or helical paths, never doing work on the particle itself.
A spinning gyroscope resists changes to its orientation. Similarly, a charged particle moving in a magnetic field "resists" going straight and curves instead, with the magnetic force acting like an invisible hand constantly pushing it sideways.
Magnetic fields are represented by field lines that form closed loops, always emerging from north poles and entering south poles. Unlike electric fields, magnetic field lines never begin or end— they always form continuous loops because there are no magnetic monopoles.
This equation, known as Gauss's Law for Magnetism, states that the net magnetic flux through any closed surface is always zero. Every field line that enters must exit, creating the characteristic dipole pattern we see in magnets.
Imagine stretching invisible rubber bands from north to south pole. The field lines behave like these bands—they want to be as short as possible, and they're always under tension, trying to pull opposite poles together.
Michael Faraday discovered that a changing magnetic field can induce an electric current in a nearby conductor. This phenomenon, known as electromagnetic induction, is the foundation of modern electrical generation and power transmission.
The induced electromotive force (EMF) is proportional to the rate of change of magnetic flux. The negative sign represents Lenz's Law: the induced current creates a magnetic field that opposes the change that produced it.
Imagine turning a water wheel by pushing water through it. The harder and faster you push the water (changing magnetic field), the faster the wheel spins (induced current). If you try to stop the wheel, it pushes back against you—just like Lenz's Law in action.