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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; $\text{1 G}={}^{}$

- 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, $\epsilon =\text{Blv}$

- 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 $B=\frac{{\mu}_{0}I}{2\mathrm{\pi r}}\text{,}$ where $I$ is the current, $r$ is the shortest distance to the wire, and ${\mu}_{0}$ is the permeability of free space

- magnetic field strength at the center of a circular loop
- defined as $B=\frac{{\mu}_{0}I}{2R}$ where $R$ is the radius of the loop

- magnetic field strength inside a solenoid
- defined as $B={\mu}_{0}\text{nI}$ where $n$ is the number of loops per unit length of the solenoid $(n=N/l\text{,}$ with $N$ being the number of loops and $l$ 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 $I$ and not $\theta \text{,}$ 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 ${\mu}_{0}=\mathrm{4\pi}\phantom{\rule{0.25em}{0ex}}\times \phantom{\rule{0.25em}{0ex}}{\text{10}}^{-7}\phantom{\rule{0.25em}{0ex}}\mathrm{T}\cdot \text{m/A}$

- 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 $\mathbf{\text{v}}$ and the fingers point in the direction of the magnetic field $\mathbf{\text{B}}\text{,}$ 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; $\text{1 T}=\frac{\text{1 N}}{\mathrm{A}\cdot \mathrm{m}}$