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The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. Measurements with microelectrodes have shown that a 0.30-nm-diameter potassium ion (K+) channel carries a current of 1.8 pA. How many potassium ions pass through if the ion channel opens for 1.0 ms?
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College Physics: A Strategic Approach (4th Edition)
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- The portion of a nerve cell thatconducts signals is called an axon. Many of the electrical properties ofaxons are governed by ion channels, which are protein molecules thatspan the axon’s cell membrane. When open, each ion channel has apore that is filled with fluid of low resistivity and connects the interiorof the cell electrically to the medium outside the cell. In contrast, thelipid-rich cell membrane in which ion channels reside has very highresistivity. Assume that a typical open ion channel spanning an axon’s membrane has a resistance of 1 * 10^11 Ω. We can model this ion channel, with its pore, as a 12-nm-long cylinder of radius 0.3 nm. What is the resistivity of the fluid in the pore? (a) 10 Ω . m; (b) 6 Ω . m; (c) 2 Ω . m; (d) 1 Ω . m.arrow_forwardTwo resistors are wired in series with a 123 V battery. The first resistor has a resistance of 6 k and the second resistor has a resistance of 1 kQ. What is the current in amperes that is leaving the positive terminal of the battery?arrow_forwardAs discussed in the chapter, a thermistor is a device whose resistance varies with temperature. At 20°C a thermistor’s resistance is 10.0 kΩ. When connected to a 1.2 V battery, the current through the thermistor increases by 30 μA as the temperature increases to 30°C. What is the thermistor’s resistance at this higher temperature?arrow_forward
- The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. Measurements with microelectrodes have shown that a 0.269 nm diameter potassium ion (K+) channel carries a current of 7.49 pA. How many potassium ions pass through if the ion channel opens for 1.48 ms? Submit Answer Tries 0/10 What is the current density (in A/m/m) in the ion channel? Submit Answer Tries 0/10arrow_forwardThe 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)?arrow_forwardOne hundred meters of a certain type of wire has a resistance of 7.2 Q. What is the resistance of 2.5 m of this wire? 0.30 2 0.18 Q 3.0 2 1.8 Q 18 Qarrow_forward
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- A light bulb is connected to a wall outlet for 5 minutes and draws an electrical current of 10 amperes from the electrical grid. How many coulombs of electrons flow through the light bulb?arrow_forwardThree resistors of resistances R1 = 14.8 Ω, R2 = 70.3 Ω, and R3 = 39.7 Ω are connected in parallel. What is the equivalent resistance (Req,p)?arrow_forwardIn the circuit shown in the diagram below, two thick wires connect a 1.5 volt battery to a Nichrome (NiCr) wire. Each thick connecting wire is 17 cm long, and has a radius of 9 mm. The thick wires are made of copper, which has 8.36e+28 mobile electrons per cubic meter, and an electron mobility of 0.00434 (m/s)/(V/m). The Nichrome wire is 8 cm long, and has a radius of 4 mm. Nichrome has 9e+28 mobile electrons per cubic meter, and an electron mobility of 7e-05 (m/s)/(V/m). What is the magnitude of the electric field in the thick copper wire? V/m What is the magnitude of the electric field in the thin Nichrome wire? V/m Copper Copper Nichromearrow_forward
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