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AC current
current that fluctuates sinusoidally with time, expressed as I = I0 sin 2πft, where I is the current at time t, I0 is the peak current, and f is the frequency in hertz
AC voltage
voltage that fluctuates sinusoidally with time, expressed as V = V0 sin 2πft, where V is the voltage at time t, V0 is the peak voltage, and f is the frequency in hertz
alternating current
(AC) the flow of electric charge that periodically reverses direction
(amp) the SI unit for current; 1 A = 1 C/s
electrical effects in and created by biological systems
direct current
(DC) the flow of electric charge in only one direction
drift velocity
the average velocity at which free charges flow in response to an electric field
electric current
the rate at which charge flows, I = ΔQt
electric power
the rate at which electrical energy is supplied by a source or dissipated by a device; it is the product of current times voltage
electrocardiogram (ECG)
usually abbreviated ECG, a record of voltages created by depolarization and repolarization, especially in the heart
microshock sensitive
a condition in which a person’s skin resistance is bypassed, possibly by a medical procedure, rendering the person vulnerable to electrical shock at currents about 1/1000 the normally required level
nerve conduction
the transport of electrical signals by nerve cells
the unit of resistance, given by 1Ω = 1 V/A
Ohm’s law
an empirical relation stating that the current I is proportional to the potential difference V, ∝ V; it is often written as I = V/R, where R is the resistance
a type of a material for which Ohm's law is valid
the electric property that impedes current; for ohmic materials, it is the ratio of voltage to current, R = V/I
an intrinsic property of a material, independent of its shape or size, directly proportional to the resistance, denoted by ρ
rms current
the root mean square of the current, I rms = I 0 / 2 I rms = I 0 / 2 , where I0 is the peak current, in an AC system
rms voltage
the root mean square of the voltage, V rms = V 0 / 2 V rms = V 0 / 2 , where V0 is the peak voltage, in an AC system
property of a membrane that allows only certain types of ions to cross it
shock hazard
when electric current passes through a person
short circuit
also known as a “short,” a low-resistance path between terminals of a voltage source
simple circuit
a circuit with a single voltage source and a single resistor
temperature coefficient of resistivity
an empirical quantity, denoted by α, which describes the change in resistance or resistivity of a material with temperature
thermal hazard
a hazard in which electric current causes undesired thermal effects
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