Physics (5th Edition)
5th Edition
ISBN: 9780321976444
Author: James S. Walker
Publisher: PEARSON
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Textbook Question
Chapter 20, Problem 92GP
Predict/Calculate Computer Keyboards Many computer keyboards operate on the principle of capacitance. As shown in Figure 20-18, each key forms a small parallel-plate capacitor whose separation is reduced when the key is depressed. (a) Does depressing a key increase or decrease its capacitance? Explain. (b) Suppose the plates for each key have an area of 47.5 mm2 and an initial separation of 0.550 mm. In addition, let the dielectric have a dielectric constant of 3.75. If the circuitry of the computer can detect a change in capacitance of 0.425 pF, what is the minimum distance a key must be depressed to be detected?
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Chapter 20 Solutions
Physics (5th Edition)
Ch. 20.1 - The electric potential in system A changes...Ch. 20.2 - Particle A accelerates from rest through a...Ch. 20.3 - The following systems consist or a point charge at...Ch. 20.4 - Figure 20-14 shows a series of equipotential...Ch. 20.5 - Two parallel-plate capacitors are identical,...Ch. 20.6 - The following systems consist of a capacitor for...Ch. 20 - In one region of space the electric potential has...Ch. 20 - If the electric field is zero in some region of...Ch. 20 - Sketch the equipotential surface that goes through...Ch. 20 - How much work is required to move a charge from...
Ch. 20 - It is known that the electric potential is...Ch. 20 - Explain why equipotentials are always...Ch. 20 - Two charges are at locations that have the same...Ch. 20 - A capacitor is connected to a battery and fully...Ch. 20 - On which of the following quantities does the...Ch. 20 - We say that a capacitor stores charge, yet the...Ch. 20 - An electron is released from rest in a region of...Ch. 20 - A uniform electric field of magnitude 3.8 105 N/C...Ch. 20 - A uniform electric field of magnitude 6.8 105 N/C...Ch. 20 - BIO Electric Potential Across a Cell Membrane In a...Ch. 20 - An old-fashioned computer monitor accelerates...Ch. 20 - A parallel-plate capacitor has plates separated by...Ch. 20 - When an ion accelerates through a potential...Ch. 20 - The Electric Potential of the Earth The Earth has...Ch. 20 - A uniform electric field with a magnitude of 6860...Ch. 20 - Predict/Calculate A spark plug in a car has...Ch. 20 - A uniform electric field with a magnitude of 1200...Ch. 20 - A Charged Battery A typical 12-V car battery can...Ch. 20 - BIO Predict/Calculate The Sodium Pump Living cells...Ch. 20 - Predict/Calculate The electric potential of a...Ch. 20 - Points A and B have electric potentials of 332 V...Ch. 20 - Predict/Explain An electron is released from rest...Ch. 20 - Calculate the speed of (a) a proton and (b) an...Ch. 20 - Ion Thrusters NASAs Deep Space 1 and Dawn...Ch. 20 - Find the potential difference required to...Ch. 20 - Predict/Calculate A particle with a mass of 3.8 g...Ch. 20 - Conduction Electrons In the microscopic view of...Ch. 20 - A proton has an initial speed of 5.5 105 m/s. (a)...Ch. 20 - In Figure 20-29, q1 = +1.8 nC and q2 = 2.1 nC, and...Ch. 20 - In Figure 20-29, it is given that, q1 = +Q. (a)...Ch. 20 - CE The charge q1 in Figure 20-29 has the value +Q....Ch. 20 - CE It is given that the electric potential is zero...Ch. 20 - The electric potential 1.6 m from a point charge q...Ch. 20 - A point charge of 9.2 C is at the origin. What is...Ch. 20 - The Bohr Atom The hydrogen atom consists of one...Ch. 20 - How far must the point charges q1 = +6.22 C and q2...Ch. 20 - Four different arrangements of point charges are...Ch. 20 - Predict/Calculate Point charges +4.1 C and 2.2C...Ch. 20 - In Figure 20-31, the charge q = 4.11 10-9C. (a)...Ch. 20 - Predict/Calculate In Figure 20-31, the charge q =...Ch. 20 - A charge of 4.07C is held fixed at the origin. A...Ch. 20 - Predict/Calculate A charge of 20.2 C is held fixed...Ch. 20 - A charge of 2.505 C is located at (3.055 m, 4.501...Ch. 20 - Predict/Calculate Figure 20-32 shows three charges...Ch. 20 - How much work must be done to move the three...Ch. 20 - (a) Find the electric potential at point P in...Ch. 20 - A square of side a has a charge +Q at each corner....Ch. 20 - A square of side a has charges +Q and Q...Ch. 20 - Predict/Explain (a) is the electric potential at...Ch. 20 - Predict/Explain Imagine sketching a large number...Ch. 20 - Two point charges are on the x axis. Charge 1 is...Ch. 20 - Figure 20-35 shows a series of equipotentials in a...Ch. 20 - Predict/Calculate Consider a region in space where...Ch. 20 - A given system has the equipotential surfaces...Ch. 20 - A given system has the equipotential surfaces...Ch. 20 - A 0.75-F capacitor is connected to a 9.0-V...Ch. 20 - It is desired that 7.7 C of charge be stored on...Ch. 20 - To operate a given flash lamp requires a charge of...Ch. 20 - Planet Capacitor It can be shown that the...Ch. 20 - A parallel-plate capacitor is made from two...Ch. 20 - A parallel-plate capacitor is constructed with...Ch. 20 - Predict/Calculate A parallel-plate capacitor has...Ch. 20 - Predict/Calculate A 72-nF parallel-plate capacitor...Ch. 20 - Predict/Calculate Consider a parallel-plate...Ch. 20 - A parallel-plate capacitor has plates of area 3.75...Ch. 20 - Predict/Calculate A parallel-plate capacitor...Ch. 20 - Suppose that after walking across a carpeted floor...Ch. 20 - (a) What plate area is required for an air-filled,...Ch. 20 - Lightning As a crude model for lightning, consider...Ch. 20 - A parallel-plate capacitor is made from two...Ch. 20 - Calculate the work done by a 9.0-V battery as it...Ch. 20 - BIO Defibrillator An automatic external...Ch. 20 - BIOPredict/Calculate Cell Membranes The membrane...Ch. 20 - A capacitor with plate area 0.0440 m2 and plate...Ch. 20 - Find the electric energy density between the...Ch. 20 - What electric field strength would store 17.5 J of...Ch. 20 - An electronic flash unit for a camera contains a...Ch. 20 - A parallel-plate capacitor has plates with an area...Ch. 20 - CE Predict/Explain A proton is released from rest...Ch. 20 - CE The plates of a parallel-plate capacitor have...Ch. 20 - CE A parallel-plate capacitor is connected to a...Ch. 20 - CE The plates of a parallel-plate capacitor have...Ch. 20 - CE A parallel-plate capacitor is connected to a...Ch. 20 - Find the difference in electric potential, V = VB ...Ch. 20 - A 0.32-F capacitor is charged by a 1.5-V battery....Ch. 20 - A charge of 22.5 C is located at (4.40 m, 6.22 m),...Ch. 20 - The Bohr Model In the Bohr model of the hydrogen...Ch. 20 - Predict/Calculate A +1.2-C charge and a 1.2-C...Ch. 20 - How much work is required to bring three protons,...Ch. 20 - A point charge Q = +87.1 C is held fixed at the...Ch. 20 - Electron Escape Speed An electron is at rest just...Ch. 20 - Quark Model of the Neutron According to the quark...Ch. 20 - A parallel-plate capacitor is charged to an...Ch. 20 - Predict/Calculate The three charges shown in...Ch. 20 - (a) In Figure 20-36 we see that the electric...Ch. 20 - BIO Predict/Calculate Electric Catfish The...Ch. 20 - Regenerative Braking Many electric cars can...Ch. 20 - Predict/Calculate Computer Keyboards Many computer...Ch. 20 - Predict/Calculate A point charge of mass 0.081 kg...Ch. 20 - BIO Cell Membranes and Dielectrics Many cells in...Ch. 20 - BIO Mitochondrial Membrane Every cell in the body...Ch. 20 - Long, long ago, on a planet far, far away, a...Ch. 20 - Rutherfords Planetary Model of the Atom In 1911,...Ch. 20 - Predict/Calculate (a) One of the Q charges in...Ch. 20 - Figure 20-38 shows a charge q = +6.77 C with a...Ch. 20 - The electric potential a distance r from a point...Ch. 20 - When the potential difference between the plates...Ch. 20 - The electric potential a distance r from a point...Ch. 20 - BIO The Electric Eel Of the many unique and...Ch. 20 - As a rough approximation, consider an electric eel...Ch. 20 - In terms of the parallel-plate model of the...Ch. 20 - How much energy is stored by an electric eel when...Ch. 20 - Predict/Calculate Referring to Example 20-9...Ch. 20 - Referring to Example 20-9 Suppose we can change...Ch. 20 - Predict/Calculate Referring to Example 20-9...
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