In a simple model of an axon conducting a nerve signal, ions move across the cell membrane through open ion channels, which act as purely resistive elements. If a typical current density (current per unit cross-sectional area) in the cell membrane is 5 mA/cm 2 when the voltage across the membrane (the action potential ) is 50 mV, what is the number density of open ion channels in the membrane? (a) 1/cm 2 ; (b) 10/cm 2 ; (c) 10/mm 2 ; (d) 100/ µ m 2 .
In a simple model of an axon conducting a nerve signal, ions move across the cell membrane through open ion channels, which act as purely resistive elements. If a typical current density (current per unit cross-sectional area) in the cell membrane is 5 mA/cm 2 when the voltage across the membrane (the action potential ) is 50 mV, what is the number density of open ion channels in the membrane? (a) 1/cm 2 ; (b) 10/cm 2 ; (c) 10/mm 2 ; (d) 100/ µ m 2 .
In a simple model of an axon conducting a nerve signal, ions move across the cell membrane through open ion channels, which act as purely resistive elements. If a typical current density (current per unit cross-sectional area) in the cell membrane is 5 mA/cm2 when the voltage across the membrane (the action potential) is 50 mV, what is the number density of open ion channels in the membrane? (a) 1/cm2; (b) 10/cm2; (c) 10/mm2; (d) 100/µm2.
If we have a material with the same electrical properties in all
directions, we define its resistivity p (the Greek letter "rho") as the ratio of
the magnitudes of the electric field E and the current density J: 0=
In vector form,
The SI unit of resistivity is one-ohm meter (1 Q-m, where the Greek letter
"omega" stands for "ohm"). One ohm equals one volt per ampere (1 0 = 1
VIA). For many materials and devices, Georg Simon Ohm found that J is
directly proportional to E at a given temperature. If so, p is constant and we
say that the material or device follows Ohm's Law or that it is ohmic.
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Calculate the resistivity of a certain metal if an electric field of 7.2 x
10-3 V/m gives a current density of 1.20 x 105 A/m2
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6.0 x 10-8 ohm-m
7.2 103 ohm-m
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O 1.2 x 105 ohm-m
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0.17 x 102 ohm-m
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The amount of charge flowing through a particular conducting wire is represented by the equation q (t) = at³ + bt? +c, where a = 5 A/s?, b = 3 A/s, and c is an
unknown constant. When t = 0.9s, the voltage across the wire is measured to be 12 V. What is the resistance of the wire in Ohms?
The resistance of a material can be calculated with the following equation:
R = ρ L A
where ρ is the resistivity, L is the length, and A is the cross-sectional area. What is the resistance of an axon’s membrane segment with a length of 1 mm (enter your answer in units of M Ω)?
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