Concept explainers
Membranes ii living cells, including those in humans, are characterized by a separation of charge across the membrane. Effectively, the membranes are thus charged capacitors with important functions related to the potential difference across the membrane. Is energy required to separate these charges m living membranes and. if so. is its source the
Figure 19.26 The semi permeable membrane of a cell has different concentrations of ions inside and out. Diffusion moves the K+ (potassium) and CI- (chloride) ions n the directions shown. until the Coulomb force halts further transfer. This results in a layer of positive charge on the outside, a layer of negative charge on the inside, and thus a voltage across the cell membrane. The membrane is normally impeftneabte to Na+ (sodium ions).
Trending nowThis is a popular solution!
Chapter 19 Solutions
College Physics
Additional Science Textbook Solutions
Chemistry: A Molecular Approach (4th Edition)
Biology: Life on Earth (11th Edition)
Campbell Biology: Concepts & Connections (9th Edition)
Campbell Biology in Focus (2nd Edition)
Microbiology: An Introduction
Campbell Essential Biology (7th Edition)
- Three capacitors are connected to a battery as shown in Figure P20.50. Their capacitances are C1 = 3C, C2 = C, and C3 = 5C. (a) What is the equivalent capacitance of this set of capacitors? (b) State the ranking of the capacitors according to the charge they store from largest to smallest. (c) Rank the capacitors according to the potential differences across them from largest to smallest. (d) What If? Assume C3 is increased. Explain what happens to the charge stored by each capacitor. Figure P20.50arrow_forwardFigure CQ16.3 shows equipotential contours in the region of space surrounding two charged conductors. Find (a) the work WAB in electron volts done by the electric force on a proton that moves from point A to point B. Similarly, find (b) WAC, (c) WAD, and (d) WAE. Figure CQ16.3arrow_forward(i) A battery is attached to several different capacitors connected in parallel. Which of the following statements is true? (a) All capacitors have the same charge, and the equivalent capacitance is greater than the capacitance of any of the capacitors in the group, (b) The capacitor with the largest capacitance carries the smallest charge, (c) The potential difference across each capacitor is the same, and the equivalent capacitance is greater than any of the capacitors in the group. (d) The capacitor with the smallest capacitance carries the largest charge. (e) The potential differences across the capacitors are the same only if the capacitances are the same, (ii) The capacitors are reconnected in series, and the combination is again connected to the battery. From the same choices, choose the one that is true.arrow_forward
- Find the charge on each of the capacitors in Figure P16.43. Figure P16.43arrow_forwardFour capacitors are connected as shown in Figure P16.48. (a) Find the equivalent capacitance between points a and b. (b) Calculate the charge on each capacitor, taking Vab = 15.0 V. Figure P16.48arrow_forwardFind the total capacitance of the combination of capacitors in Figure 19.33. Figure 19.33 A combination of series and parallel connections of capacitors.arrow_forward
- The network of capacitors shown below are all uncharged when a 300-V potential is applied between points A and B with the switch S open, (a) What is the Potential difference VE-VD? (b) What is the potential at point E after the switch is closed? (c) How much charge flows through the switch after it is closed?arrow_forward(a) How much energy is stored in the electrical fields in the capacitors (in total) shown below? (b) Is this energy equal to the work done by the 400-V source in charging the capacitors?arrow_forwardAssume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed pulse duration = 50.0 m/s 2.0 103 s = 0.10 m). In the resting state, the outer surface of the axon wall is charged positively with K+ ions and the inner wall has an equal and opposite charge of negative organic ions, as shown in Figure P18.43. Model the axon as a parallel-plate capacitor and take C = 0A/d and Q = C V to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.0 108 m, axon radius r = 1.0 101 m, and cell-wall dielectric constant = 3.0. (a) Calculate the positive charge on the outside of a 0.10-m piece of axon when it is not conducting an electric pulse. How many K+ ions are on the outside of the axon assuming an initial potential difference of 7.0 102 V? Is this a large charge per unit area? Hint: Calculate the charge per unit area in terms of electronic charge e per squared (2). An atom has a cross section of about 1 2 (1 = 1010 m). (b) How much positive charge must flow through the cell membrane to reach the excited state of + 3.0 102 V from the resting state of 7.0 102 V? How many sodium ions (Na+) is this? (c) If it takes 2.0 ms for the Na+ ions to enter the axon, what is the average current in the axon wall in this process? (d) How much energy does it take to raise the potential of the inner axon wall to + 3.0 102 V, starting from the resting potential of 7.0 102 V? Figure P18.43 Problem 43 and 44.arrow_forward
- (a) Find the equivalent capacitance between points a and b for the group of capacitors connected as shown in Figure P20.44. Take C1 = 5.00 F, C2 = 10.0 F, and C3 = 2.00 F. (b) What charge is stored on C3 if the potential difference between points a and b is 60.0 V? Figure P20.44arrow_forwardIf three unequal capacitors, initially uncharged, are connected in series across a battery, which of the following statements is true? (a) The equivalent capacitance is greater than any of the individual capacitances, (b) The largest voltage appeal's across the smallest capacitance, (c) The largest voltage appears across the largest capacitance. (d) The capacitor with the largest capacitance has the greatest charge, (e) The capacitor with the smallest capacitance has the smallest charge.arrow_forwardWhat If? The two capacitors of Problem 13 (C1 = 5.00 F and C2 = 12.0 F) are now connected in series and to a 9.00-Y battery. Find (a) the equivalent capacitance of the combination. (b) the potential difference across each capacitor, and (c) the charge on each capacitor.arrow_forward
- College PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegeCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
- Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning