Glossary
Circular Motion (in magnetic field)
The path taken by a charged particle when its velocity is perfectly perpendicular to a uniform magnetic field, as the magnetic force acts as a centripetal force. [1, 6, 25, 31]
Example:
In a mass spectrometer, ions follow a path of circular motion within a magnetic field, allowing their mass-to-charge ratio to be determined. [1]
Coulomb's Law
A fundamental law stating that the electrostatic force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them. [7, 10, 28]
Example:
Calculating the repulsive force between two protons in an atomic nucleus requires applying Coulomb's Law.
Dipole Field (Magnetic)
The magnetic field pattern produced by two opposite magnetic poles, like a bar magnet or the Earth, where field lines emerge from the north pole and enter the south pole. [9]
Example:
The Earth's magnetic field, which protects us from solar radiation, is an example of a large-scale dipole field.
Electric Field (E)
A vector field that describes the electric force per unit positive test charge at any point in space, originating from electric charges. [2, 11, 13]
Example:
The region around a charged balloon where it can attract small pieces of paper is an electric field.
Electric Field Lines
Imaginary lines used to visualize an electric field, where the direction of the line indicates the direction of the force on a positive test charge, and their density indicates field strength. [2, 8, 16, 17]
Example:
Drawing electric field lines around a positive point charge shows them radiating outwards, indicating the direction a positive charge would move. [8]
Electric Force
The attractive or repulsive force between any two charged objects, described by Coulomb's Law or as the product of charge and electric field strength. [7, 28]
Example:
When you rub a balloon on your hair, the electric force causes your hair to stand on end due to charge transfer.
Electromagnetic Induction
The process where a changing magnetic field through a conductor induces an electromotive force (voltage) and, consequently, an electric current. [3]
Example:
Wireless charging pads for phones work through electromagnetic induction, transferring energy from a coil in the pad to a coil in the phone. [35]
Electromagnetism
The unified study of electricity and magnetism, showing how a changing electric field produces a magnetic field, and a changing magnetic field produces an electric field. [3]
Example:
The operation of an MRI machine relies heavily on principles of electromagnetism to create detailed images of the body's interior.
Electromotive Force (EMF)
The voltage induced in a circuit by a changing magnetic flux, representing the energy per unit charge supplied by a source to drive current. [34]
Example:
A battery provides an electromotive force to push electrons through a circuit, creating a current.
Faraday's Law
States that the magnitude of the induced electromotive force (EMF) in a circuit is proportional to the rate of change of magnetic flux through the circuit. [34]
Example:
When you wave a magnet quickly past a coil of wire, Faraday's Law explains why a current is generated in the wire. [34]
Generators
Devices that convert mechanical energy into electrical energy by rotating a coil of wire within a magnetic field, inducing an electromotive force. [35]
Example:
Hydroelectric power plants use large generators to convert the kinetic energy of falling water into electricity for homes.
Helical Motion (in magnetic field)
The spiral path taken by a charged particle when its velocity has components both parallel and perpendicular to a uniform magnetic field. [1, 6, 18, 29, 30]
Example:
Charged particles from the sun trapped by Earth's magnetic field often exhibit helical motion as they spiral along the field lines towards the poles, creating auroras. [1]
Lenz's Law
States that the direction of an induced current in a conductor will always be such that it opposes the change in magnetic flux that produced it, reflecting energy conservation. [15]
Example:
If you drop a strong magnet through a copper pipe, Lenz's Law causes it to fall slowly due to the opposing induced currents.
Lorentz Force Law
Describes the total force exerted on a point charge due to both electric and magnetic fields, with the magnetic component given by F = qvBsin(θ). [12, 15]
Example:
The path of an electron beam in a cathode ray tube is precisely controlled by the Lorentz Force Law, which dictates its deflection by electric and magnetic fields.
Magnetic Fields
A vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials, exerting a force on them. [5, 12, 15]
Example:
Birds are thought to navigate using Earth's magnetic fields, sensing their direction and strength. [1]
Magnetic Flux (ΦB)
A measure of the total number of magnetic field lines passing through a given area, calculated as the product of the magnetic field strength, the area, and the cosine of the angle between them. [3, 19]
Example:
To maximize the induced current in a generator, the coil is designed to maximize the change in magnetic flux as it rotates.
Magnetic Forces
The force exerted by a magnetic field on a moving electric charge or a current-carrying wire, always perpendicular to both the velocity of the charge and the magnetic field. [12, 26]
Example:
The deflection of charged particles in a particle accelerator is controlled by precisely applied magnetic forces.
Magnetic Moment
A vector quantity that describes the strength and orientation of a magnetic dipole, such as a current loop or the intrinsic spin of an electron. [24]
Example:
The alignment of a compass needle with Earth's magnetic field is due to its magnetic moment interacting with the field.
Magnetic Monopoles
Hypothetical isolated magnetic poles (north or south) that have not been observed in nature, unlike electric charges which can exist as monopoles. [4, 9, 14]
Example:
Despite extensive searches, physicists have yet to discover any evidence of magnetic monopoles existing freely in nature.
Magnetism
The phenomenon by which materials exert attractive or repulsive forces on other materials, often due to the motion of electric charges. It is a fundamental force closely related to electricity. [4]
Example:
A compass needle aligns itself with Earth's magnetism, pointing towards the magnetic north pole. [1]
Magnets
Objects or materials, typically made of ferromagnetic elements like iron, cobalt, or nickel, that produce their own persistent magnetic fields. [1, 3, 22]
Example:
Refrigerator magnets hold notes to the door because of their inherent magnetic properties. [24]
Monopole Field (Magnetic)
A theoretical magnetic field pattern that would be produced by an isolated magnetic north or south pole, if such monopoles existed.
Example:
If monopole fields existed, magnetic field lines would not form closed loops but would originate from or terminate at these isolated poles.
Motors
Devices that convert electrical energy into mechanical energy by using the magnetic force exerted on a current-carrying coil in a magnetic field.
Example:
The spinning blades of a fan are powered by an electric motor that converts electrical energy into rotational motion.
Newtons (N)
The SI unit of force, defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second squared. [27]
Example:
Pushing a shopping cart requires applying a certain number of Newtons of force.
Newtons per Coulomb (N/C)
The SI unit for electric field strength, representing the force exerted per unit of electric charge. [2, 8, 15]
Example:
If an electric field has a strength of 100 Newtons per Coulomb, it means a 1 Coulomb charge would experience 100 Newtons of force.
Right-Hand Rule (for magnetic field direction)
A mnemonic used to determine the direction of the magnetic field around a current-carrying wire: point your thumb in the direction of current, and your curled fingers indicate the field direction. [3, 5]
Example:
Using the Right-Hand Rule helps determine that the magnetic field around a straight wire carrying current upwards forms concentric circles counter-clockwise. [3]
Right-Hand Rule (for magnetic force direction)
A mnemonic used to determine the direction of the magnetic force on a positive moving charge: point fingers in velocity, curl towards magnetic field, thumb points to force. [3, 5, 25]
Example:
When an electron enters a magnetic field, applying the Right-Hand Rule (and then reversing for negative charge) helps predict its deflection. [5]
Tesla (T)
The SI unit for magnetic field strength, representing one Weber per square meter. [1, 3, 5, 15]
Example:
A strong refrigerator magnet might have a magnetic field strength of about 0.01 Tesla.
Tesla square meter (T·m²)
An alternative SI unit for magnetic flux, equivalent to the Weber, representing the product of magnetic field strength in Teslas and area in square meters. [33, 34]
Example:
If a 0.5 T magnetic field passes perpendicularly through a 2 m² area, the magnetic flux is 1 Tesla square meter.
Transformers
Devices that transfer electrical energy between two or more circuits through electromagnetic induction, typically used to change the voltage of alternating current. [15]
Example:
The large boxes on power poles are transformers that step down high voltage electricity from power lines to a safer voltage for household use.
Volts (V)
The SI unit for electromotive force (EMF) and electric potential difference, representing one joule of energy per coulomb of charge. [27]
Example:
A standard AA battery typically provides 1.5 Volts of potential difference.
Weber (Wb)
The SI unit for magnetic flux, defined as one Tesla-meter squared. [3, 19, 20, 33, 34]
Example:
A strong electromagnet might produce a Weber of magnetic flux through a large loop of wire.