Fields & Magnetism
12 concepts in Physics
Fields and magnetism reveal how electric charges and magnets influence each other across empty space, without any physical contact. Students learn that every charge creates an electric field around it, and that this field exerts forces on other charges — an idea quantified by Coulomb's law. They study electric potential and potential difference as measures of the energy landscape created by charges. The topic extends to magnetic fields, which are produced by moving charges and electric currents. Electromagnetic induction — the discovery that a changing magnetic field creates an electric current — is one of the most consequential findings in physics, underpinning generators, transformers, and modern power grids. Faraday's law and Lenz's law give students the quantitative tools to analyze induction. These concepts connect electricity and magnetism into a unified framework that eventually leads to Maxwell's equations and an understanding of light itself.
Suggested learning path: Begin with electric fields and Coulomb's law, then study electric potential and potential difference, move to magnetic fields and forces on current-carrying conductors, and finally explore electromagnetic induction through Faraday's and Lenz's laws.
Electric Field
A region around a charged object where other charges experience a force. Measured in newtons per coulomb (N/C) or volts per meter (V/m).
Coulomb's Law
The force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
Electric Potential
The electric potential energy per unit charge at a point in an electric field. Measured in volts (V).
Potential Difference
The difference in electric potential between two points, equal to the work done per unit charge moving between them.
Magnetic Field
A region around a magnet or moving charge where magnetic forces act. Measured in tesla (T).
Magnetic Force
The force exerted on a moving charge or current-carrying conductor by a magnetic field.
Electromagnetic Induction
The production of voltage (EMF) in a conductor when the magnetic flux through it changes.
Faraday's Law
The induced EMF in a circuit equals the negative rate of change of magnetic flux through the circuit.
Lenz's Law
The direction of an induced current is always such that it opposes the change in magnetic flux that produced it.
Generator
A device that converts mechanical energy into electrical energy by rotating a coil in a magnetic field, using electromagnetic induction.
Transformer
A device that changes the voltage of alternating current by using two coils wound around a shared iron core.
Electric Motor
A device that converts electrical energy into mechanical energy (rotation) using the force on a current-carrying conductor in a magnetic field.