A defibrillator is designed to pass a large current through a patient’s torso in order to stop dangerous heart rhythms. Its key part is a capacitor that is charged to a high voltage. The patient’s torso plays the role of a resistor in an RC circuit. When a switch is closed, the capacitor discharges through […]
A cell membrane has a resistance and a capacitance and thus a characteristic time constant. Part A What is the time constant of a 9.0-nm-thick membrane surrounding a 0.040-mm-diameter spherical cell? Assume the resistivity of the cell membrane as 3.6×10^7 Ω⋅m and the dielectric constant is approximately 9.0. Express your answer with the appropriate units.
A 8.7-nm-thick cell membrane undergoes an action potential that follows the curve in (Figure 1) . Part A What is the strength of the electric field inside the membrane just before the action potential? Express your answer to two significant figures and include the appropriate units. Part B What is the strength of the electric […]
Consider the combination of capacitors shown in the diagram, where C1 = 3.00 μF , C2 = 11.0 μF , C3 = 3.00 μF , and C4 = 5.00 μF . (Figure 1) Part A Find the equivalent capacitance CA of the network of capacitors. Express your answer in microfarads. Part B Two capacitors of […]
Learning Goal: To practice Tactics Box 23.1 Using Kirchhoff’’loop law. Circuit analysis is based on Kirchhoff’s laws, which can be summarized as follows: Kirchhoff’s junction law says that the total current into a junction must equal the total current leaving the junction. Kirchhoff’s loop law says that if we add all of the potential differences […]
The electric field inside a 35-cm-long copper wire is 0.018 V/m . Part A What is the potential difference between the ends of the wire? Express your answer using two significant figures.
In a typical lightning strike, 2.5 C flows from cloud to ground in 0.20 ms. Part A What is the current during the strike?
An immersion heater used to boil water for a single cup of tea plugs into a 120 V outlet and is rated at 250 W . Suppose your super-size, super-insulated tea mug contains 400 g of water at a temperature of 23 ∘C. You can ignore the energy needed to raise the temperature of the […]
Variations in the resistivity of blood can give valuable clues to changes in the blood’s viscosity and other properties. The resistivity is measured by applying a small potential difference and measuring the current. Suppose a medical device attaches electrodes into a 1.5-mm-diameter vein at two points 5.0 cm apart. Part A What is the blood […]
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 […]