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Glossary

# Glossary

Ampere’s law
the physical law that states that the magnetic field around an electric current is proportional to the current; each segment of current produces a magnetic field like that of a long straight wire, and the total field of any shape current is the vector sum of the fields due to each segment
B-field
another term for magnetic field
Biot-Savart law
a physical law that describes the magnetic field generated by an electric current in terms of a specific equation
direction of magnetic field lines
the direction that the north end of a compass needle points
gauss
G, the unit of the magnetic field strength; $1 G=10–4T1 G=10–4T size 12{"1 G"="10" rSup { size 8{ - 4} } `T} {}$
Hall effect
the creation of voltage across a current-carrying conductor by a magnetic field
Hall emf
the electromotive force created by a current-carrying conductor by a magnetic field, $ε=Blvε=Blv size 12{ε= ital "Blv"} {}$
Lorentz force
the force on a charge moving in a magnetic field
magnetic field
the representation of magnetic forces
magnetic field lines
the pictorial representation of the strength and the direction of a magnetic field
magnetic field strength (magnitude) produced by a long straight current-carrying wire
defined as $B=μ0I2πr,B=μ0I2πr,$ where $II$ is the current, $rr$ is the shortest distance to the wire, and $μ0μ0$ is the permeability of free space
magnetic field strength at the center of a circular loop
defined as $B=μ0I2RB=μ0I2R$ where $RR$ is the radius of the loop
magnetic field strength inside a solenoid
defined as $B=μ0nIB=μ0nI$ where $nn$ is the number of loops per unit length of the solenoid $(n=N/l,(n=N/l,$ with $NN$ being the number of loops and $ll$ the length)
magnetic force
the force on a charge produced by its motion through a magnetic field; the Lorentz force
magnetic resonance imaging (MRI)
a medical imaging technique that uses magnetic fields create detailed images of internal tissues and organs
magnetocardiogram (MCG)
a recording of the heart’s magnetic field as it beats
magnetoencephalogram (MEG)
a measurement of the brain’s magnetic field
Maxwell’s equations
a set of four equations that describe electromagnetic phenomena
meter
common application of magnetic torque on a current-carrying loop that is very similar in construction to a motor; by design, the torque is proportional to $II$ and not $θ,θ,$ so the needle deflection is proportional to the current
motor
loop of wire in a magnetic field; when current is passed through the loops, the magnetic field exerts torque on the loops, which rotates a shaft; electrical energy is converted to mechanical work in the process
north magnetic pole
the end or the side of a magnet that is attracted toward Earth’s geographic North Pole
nuclear magnetic resonance (NMR)
a phenomenon in which an externally applied magnetic field interacts with the nuclei of certain atoms
permeability of free space
the measure of the ability of a material, in this case free space, to support a magnetic field; the constant $μ0=4π×10−7T⋅m/Aμ0=4π×10−7T⋅m/A$
right-hand rule 1 (RHR-1)
the rule to determine the direction of the magnetic force on a positive moving charge: when the thumb of the right-hand points in the direction of the charge’s velocity $vv size 12{v} {}$ and the fingers point in the direction of the magnetic field $B,B,size 12{B} {}$ then the force on the charge is perpendicular and away from the palm; the force on a negative charge is perpendicular and into the palm
right-hand rule 2 (RHR-2)
a rule to determine the direction of the magnetic field induced by a current-carrying wire: Point the thumb of the right-hand in the direction of current, and the fingers curl in the direction of the magnetic field loops
solenoid
a thin wire wound into a coil that produces a magnetic field when an electric current is passed through it
south magnetic pole
the end or the side of a magnet that is attracted toward Earth’s geographic south pole
tesla
T, the SI unit of the magnetic field strength; $1 T=1 NA⋅m1 T=1 NA⋅m$