5. An oil drop of mass 4.95 x 10-15 kg is balanced between two large, horizontal parallel plates 1.0 cm apart, maintained at a potential difference of 510 V. The upper plate is positive. Calculate the charge on the drop, both in coulombs and as a multiple of the elementary charge, and state whether there is an excess or deficit of electrons.

5. An oil drop of mass 4.95 x 10-15 kg is balanced between two large, horizontal parallel plates 1.0 cm apart, maintained at a potential difference of 510 V. The upper plate is positive. Calculate the charge on the drop, both in coulombs and as a multiple of the elementary charge, and state whether there is an excess or deficit of electrons.

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter19: Electric Potential And Electric Field

Section: Chapter Questions

Problem 10PE: Integrated Concepts Fusion probability is greatly enhanced when appropriate nuclei are brought close...

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Integrated Concepts The classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. In it, oil drops were suspended against the gravitational force by a vertical electric field. (See Figure 18.58.) Given the oil drop to be 1.00 m in radius and have a density of 920 kg/m3: Find the weight of the drop. (b) If the drop has a single excess electron, find the electric field strength needed to balance its weight.
List all the possible values of s and msfor an electron. Are there particles for which these values are different? The same?
When p- and n-type materials are joined, why is a uniform electric field generated near the junction?
In the Millikan oil-drop experiment illustrated in Figure 15.21, an atomizer (a sprayer with a fine nozzle) is used to introduce many tiny droplets of oil between two oppositely charged parallel metal plates. Some of the droplets pick up one or more excess electrons. The charge on the plates is adjusted so that the electric force on the excess electrons exactly balances the weight of the droplet. The idea is to look for a droplet dial has the smallest electric force and assume it has only one excess electron. This strategy lets the observer measure the charge on the electron. Suppose we are using an electric field of 3 104 N/C. The charge on one electron is about 1.6 1019 C. Estimate the radius of an oil drop of density 858 kg/m5 for which its weight could be balanced by the electric force of this field on one electron. (Problem 42 is courtesy of E.F. Redish. For more problems of this type, visit www.physics.umd.cdu/pcrg/.)
In 1911, Ernest Rutherford and his assistants Geiger and Marsden conducted an experiment in which they scattered alpha particles (nuclei of helium atoms) from thin sheets of gold. An alpha particle, having charge +2e and mass 6.64 10-27 kg, is a product of certain radioactive decay's. The results of the experiment led Rutherford to the idea that most of an atoms mass is in a very small nucleus, with electrons in orbit around it. (This is the planetary model of the atom, which well study in Chapter 42.) Assume an alpha particle, initially very far from a stationary gold nucleus, is fired with a velocity of 2.00 107 m/s directly toward the nucleus (charge +79e). What is the smallest distance between the alpha particle and the nucleus before the alpha particle reverses direction? Assume the gold nucleus remains stationary.
Why are some materials very good conductors and others very poor conductors?
Calculate the speed of (a) an electron and (b) a proton with a kinetic energy of 1.00 electron volt (eV). (c) Calculate the average translational kinetic energy in cV of a 3.00 102 K ideal gas particle. (Recall from Topic 10 that 12mv2 = 32kBT.)
Integrated Concepts (a) In Figure 18.59, four equal charges q lie on the corners of a square. A fifth charge Q is on a mass m directly above the center of the square, at a height equal to the length d of one side of the square. Determine the magnitude of q in terms of Q. m, and d, if the Coulomb force is to equal the weight of m. (b) Is this equilibrium stable or unstable? Discuss.
Integrated Concepts Fusion probability is greatly enhanced when appropriate nuclei are brought close together, but mutual Coulomb repulsion must be overcome. This can be done using the kinetic energy of high-temperature gas ions or by accelerating the nuclei toward one another. (a) Calculate the potential energy of two singly charged nuclei separated by 1 .00 10-12 m by finding the voltage of one at that distance and multiplying by the charge of the other. (b) At what temperature will atoms of a gas have an average kinetic energy equal to this needed electrical potential energy?
What is the Hall effect and what is it used for?
The planetary model of the atom pictures electrons orbiting the atomic nucleus much as planets orbit the Sun. In this model you can view hydrogen, the simplest atom, as having a single electron in a circular orbit 1.061010 m in diameter. (a) If the average speed of the electron in this orbit is known to be 2.20106 m/s, calculate the number of revolutions per second it makes about the nucleus. (b) What is the electron's average velocity?
The liquid-drop model of the atomic nucleus suggests high-energy oscillations of certain nuclei can split the nucleus into two unequal fragments plus a few neutrons. The fission products acquire kinetic energy from their mutual Coulomb repulsion. Assume the charge is distributed uniformly throughout the volume of each spherical fragment and. immediately before separating each fragment is at rest and their surfaces are in contact. The electrons surrounding the nucleus can be ignored. Calculate the electric potential energy (in electron volts) of two spherical fragments from a uranium nucleus having the following charges and radii: 38e and 5.50 10-15 m. and 54e and 6.20 10-15 m.