Which of the following is a correct statement? Select one O The electric energy density stored in any electric field is proportional to E O The currents passing through electronic devices connected in parallel are equal O The electric current density is a vector quantity O The capacitance of a capacitor determines its ability to store charge, and thus it can be positive quantity or negative quantity O The capacitance of a single isolated spherical conductor with radius R is proportional to R

Which of the following is a correct statement? Select one O The electric energy density stored in any electric field is proportional to E O The currents passing through electronic devices connected in parallel are equal O The electric current density is a vector quantity O The capacitance of a capacitor determines its ability to store charge, and thus it can be positive quantity or negative quantity O The capacitance of a single isolated spherical conductor with radius R is proportional to R

Physics for Scientists and Engineers

10th Edition

ISBN:9781337553278

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter25: Capacitance And Dielectrics

Section: Chapter Questions

Problem 33AP: You are working in a laboratory, using very sensitive measurement equipment. Your supervisor has...

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A Van de Graaff generator is one of the original particle accelerators and can be used to accelerate charged particles like protons or electrons. You may have seen it used to make human hair stand on end or produce large sparks. One application of the Van de Graaff generator is to create X-rays by bombarding a hard metal target with the beam. Consider a beam of protons at 1.00 keV and a current of 5.00 mA produced by the generator, (a) What is the speed of the protons? (b) How many protons are produced each second?
(a) A defibrillator passes 12.0 A of current through the torso of a person for 0.0100 s. How much charge moves? (b) How many electrons pass through the wires connected to the patient? (See figure two problems earlier.)
Consider the circuit below. The capacitor has a capacitance of 10 mF. The switch is closed and after a long time the capacitor is fully charged, (a) What is the current through each resistor a long time after the switch is closed? (b) What is the voltage across each resistor a long rime after the switch is closed? (c) What is the voltage across the capacitor a long time after the switch is closed? (d) What is the charge on the capacitor a long time after the switch is closed? (e) The switch is then opened. The capacitor discharges through the resistors. How long from the time before the current drops to one fifth of the initial value?
You have a faculty position at a community college and are teaching a class in automotive technology. You are deep in a discussion of using jumper cables to start a car with a dead battery from a car with a fresh battery. You have drawn the circuit diagram in Figure P27.16 to explain the process. The battery on the left is the live battery in the correctly functioning car, with emf and internal resistance RL, where the L subscript refers to live. Its terminals are connected directly across those of the dead battery, in the middle of the diagram, with emf and internal resistance RD, where the D subscript refers to dead. Then, the starter in the car with the dead battery is activated by closing the ignition switch, allowing the car to start. The resistance of the starter is RS. A student raises his hand and asks, So is the dead battery being charged while the starter is operating? How do you respond? Figure P27.16
You are working in a laboratory, using very sensitive measurement equipment. Your supervisor has explained that the equipment is also very sensitive to electrical discharge from human operators. Specification tables for the equipment indicate that an electrical discharge providing even a very small amount of energy of 250 J is enough to damage the equipment. Your supervisor wants to install an apparatus that will be used to remove the electrical charge from individuals bodies before they touch the equipment. To do this, she asks you to estimate (a) the capacitance of the human body and determine (b) the charge on the body and (c) the electric potential of the body, relative to a point infinitely far away, corresponding to the energy transfer that will damage the equipment.
A 12-V car battery is used to power a 20.00-W, 12.00-V lamp during the physics club camping trip/star party. The cable to the lamp is 2.00 meters long, 14-gauge copper wire with a charge density of n=9.501028m3 . (a) What is the current draw by the lamp? (b) How long would it take an electron to get from the battery to the lamp?
You have a faculty position at a community college and are m (caching a class in automotive technology. You are deep in a discussion of using jumper cables to start a car with a dead battery from a car with a fresh battery. You have drawn the circuit diagram in Figure P27.16 to explain the process. The battery on the left is the live batten- in the correctly functioning car, with emf and internal resistance RL where the L. subscript refers to live. Its terminals are connected directly across those of the dead battery, in the middle of the diagram, with emf and internal resistance RD where the D subscript refers to "dead Then, the starter in the car with the dead battery is activated by closing the ignition switch, allowing the car to start. The resistance of the starter is Rs. A student raises his hand and asks, So is the dead battery being charged while the starter is operating? How do you respond?
Study Figure 23.3 and the accompanying text discussion of charging by induction. When the grounding wire is touched to the rightmost point on the sphere in Figure 23.3c, electrons are drained away from the sphere to leave the sphere positively charged. Suppose the grounding wire is touched to the leftmost point on the sphere instead. (a) Will electrons still drain away, moving closer to the negatively charged rod as they do so? (b) What kind of charge, if any, remains on the sphere?
The Van de Graaff generator, diagrammed in Figure P26.24, is an electrostatic device that can raise the metal dome to a high voltage. The dome of such a generator is seen on the left in Figure 22.1a. In the device, charge is delivered continuously to the high-potential dome by means of a moving belt of insulating material. The belt is charged at point by means of a discharge between comb-like metallic needles and a grounded grid. The needles are maintained at a positive electric potential of typically 104 V. The positive charge on the moving belt is transferred to the dome by a second comb of needles at point . Because the electric field inside the dome is negligible, the positive charge on the belt is easily transferred to the dome from its interior regardless of its potential. Suppose the generator is operating so that the potential difference between the high potential dome and the charging needles at is 15.0 kV. Calculate the power required to drive the belt against electrical forces at an instant when the effective current delivered to the dome is 500 A. Figure P26.24
Construct Your Own Problem Consider a battery used to supply energy to a cellular phone. Construct a problem in which you determine the energy that must be supplied by the battery, and then calculate the amount of charge it must be able to move in order to supply this energy. Among the things to be considered are the energy needs and battery voltage. You may need to look ahead to interpret manufacturer’s battery ratings in ampere hours as energy in joules.
Referring to Figure CQ28.6, describe what happens to the lightbulb after the switch is closed. Assume the capacitor has a large capacitance and is initially uncharged. Also assume the light illuminates when connected directly across the battery terminals.
A variable air capacitor used in a radio tuning circuit is made of N semicircular plates, each of radius R and positioned a distance d from its neighbors, to which it is electrically connected. As shown in Figure P25.5, a second identical set of plates is enmeshed with the first set. Each plate in the second set is halfway between two plates of the First set. The second set can rotate as a unit. Determine the capacitance as a function of the angle of rotation , where = 0 corresponds to the maximum capacitance. Figure P25.5