 University Physics Volume 2

# Key Terms

### Key Terms

ampere (amp)
SI unit for current; $1A=1C/s1A=1C/s$
circuit
complete path that an electrical current travels along
conventional current
current that flows through a circuit from the positive terminal of a battery through the circuit to the negative terminal of the battery
critical temperature
temperature at which a material reaches superconductivity
current density
flow of charge through a cross-sectional area divided by the area
diode
nonohmic circuit device that allows current flow in only one direction
drift velocity
velocity of a charge as it moves nearly randomly through a conductor, experiencing multiple collisions, averaged over a length of a conductor, whose magnitude is the length of conductor traveled divided by the time it takes for the charges to travel the length
electrical conductivity
measure of a material’s ability to conduct or transmit electricity
electrical current
rate at which charge flows, $I=dQdtI=dQdt$
electrical power
time rate of change of energy in an electric circuit
Josephson junction
junction of two pieces of superconducting material separated by a thin layer of insulating material, which can carry a supercurrent
Meissner effect
phenomenon that occurs in a superconducting material where all magnetic fields are expelled
nonohmic
type of a material for which Ohm’s law is not valid
ohm
$(Ω)(Ω)$ unit of electrical resistance, $1Ω=1V/A1Ω=1V/A$
Ohm’s law
empirical relation stating that the current I is proportional to the potential difference V; it is often written as $V=IRV=IR$, where R is the resistance
ohmic
type of a material for which Ohm’s law is valid, that is, the voltage drop across the device is equal to the current times the resistance
resistance
electric property that impedes current; for ohmic materials, it is the ratio of voltage to current, $R=V/IR=V/I$
resistivity
intrinsic property of a material, independent of its shape or size, directly proportional to the resistance, denoted by $ρρ$
schematic
graphical representation of a circuit using standardized symbols for components and solid lines for the wire connecting the components
SQUID
(Superconducting Quantum Interference Device) device that is a very sensitive magnetometer, used to measure extremely subtle magnetic fields
superconductivity
phenomenon that occurs in some materials where the resistance goes to exactly zero and all magnetic fields are expelled, which occurs dramatically at some low critical temperature $(TC)(TC)$
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