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Four identical metallic objects carry the following charges: +1.6 \(+6.2,-4.8,\) and \(-9.4 \mu \mathrm{C} .\) The objects are brought simultaneously into \(\mathrm{con}-\) tact, so that each touches the others. Then they are separated. (a) What is the final charge on each object? (b) How many electrons (or protons) make up the final charge on each object?

Short Answer

Expert verified
Each object has a final charge of \(-1.6\, \mu\text{C}\), consisting of \(10^{13}\) excess electrons.

Step by step solution

01

Calculate the Total Charge

To find the final charge on each object, we first need to determine the total charge when all four objects are brought into contact. Add the charges of all four objects:\[ +1.6 + 6.2 - 4.8 - 9.4 = -6.4 \, \mu\text{C} \]
02

Determine the Charge Per Object

After being brought into contact, the charge distributes evenly among the four objects. Divide the total charge by the number of objects (4):\[ \frac{-6.4 \, \mu\text{C}}{4} = -1.6 \, \mu\text{C} \] Thus, each object has a charge of \(-1.6 \, \mu\text{C}\) after separation.
03

Convert Charge to Number of Electrons

To find how many electrons (or protons) make up the charge, convert the charge from microcoulombs to coulombs and then divide by the charge of a single electron (or proton), which is approximately \(1.6 \times 10^{-19} \text{C}\). Convert \(-1.6 \, \mu\text{C}\) to \(-1.6 \times 10^{-6} \text{C}\):\[ \text{Number of electrons} = \frac{-1.6 \times 10^{-6} \text{C}}{1.6 \times 10^{-19} \text{C/electron}} = 10^{13} \text{ electrons} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Charge distribution
When we talk about charge distribution, we refer to how electric charge is spread over an area, volume, or among objects. In electrostatics, charge distribution is critical because it influences how objects interact electronically. Instead of the charges remaining solitary units, they distribute themselves when objects come into contact. This interaction and redistribution is governed by the principle that charge seeks to minimize potential energy by spreading evenly across conducting objects.

Consider the scenario where four metallic objects are each carrying different charges, and they are brought into contact. Metallic objects are typically good conductors, which means charge can move freely across their surfaces. When these objects touch, their collective charge adds up and then, thanks to their conductive nature, redistributes evenly across all of them. This equal charge distribution results in each object carrying the same amount of charge after separation.

In our example, the initial charges add up to a total charge. After being in contact, dividing this total charge by the number of objects (four in this case) gives the charge per object. Such redistribution is key in determining how the objects will interact with other charged bodies later.
Coulomb's law
Coulomb's law is a foundational principle in electrostatics describing the force acting between electrically charged objects. It's similar to Newton's law of gravitation but instead deals with electric charges. According to Coulomb's law, the force (\(F\)) between two charges (\(q_1\) and \(q_2\)) is proportional to the magnitudes of the charges and inversely proportional to the square of the distance (\(r\)) between their centers:\[ F = k \frac{|q_1 q_2|}{r^2} \]where \(k\) is Coulomb's constant (~8.99 x 10^9 N·m²/C²).

This law helps in predicting how charged objects will interact. In our context of charge distribution among four metallic objects, understanding how Coulomb's law works is crucial after they are separated. The redistributed charge on each object will determine the magnitude and direction of forces they experience from other charges in their surroundings.

This fundamental relationship aids in determining the electrostatic interactions, as it connects the concept of charge distribution not only to the redistribution process but also to the forces at play afterward, following separation.
Electron charge
Every electron carries a fundamental charge, which is approximately \(-1.6 \times 10^{-19}\) Coulombs. This value is crucial when calculating the number of electrons that contribute to a particular charge. In electrostatic problems, often we deal with macroscopic quantities of charge, but these originate from the sum of innumerable tiny electron charges.

In our exercise involving four metallic objects, after redistributing the charges evenly among them, each object ends up with a charge of \(-1.6 \, \mu\text{C}\). This charge results from the net balance of lost and gained electrons during the charge distribution process.

To understand how many electrons correspond to this charge, you convert the charge in microcoulombs to coulombs and then divide by the magnitude of the elementary charge (charge per electron), calculated by:
  • First, convert microcoulombs to coulombs: \(-1.6 \, \mu\text{C} = -1.6 \times 10^{-6} \, \text{C}\)
  • Divide the charge by the charge of a single electron (\(1.6 \times 10^{-19} \, \text{C/electron}\))
  • This gives approximately \(10^{13}\) electrons, revealing the immense number of electrons responsible for even small charges.
Understanding electron charge not only helps with comprehending how charges interact but also provides insight into the quantitative nature of microscopic electrostatic phenomena.

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Most popular questions from this chapter

At a distance \(r_{1}\) from a point charge, the magnitude of the electric field created by the charge is \(248 \mathrm{N} / \mathrm{C}\). At a distance \(r_{2}\) from the charge, the field has a magnitude of \(132 \mathrm{N} / \mathrm{C}\). Find the ratio \(r_{2} / r_{1}\).

Four identical metal spheres have charges of \(q_{\Lambda}=-8.0 \mu \mathrm{C}, q_{\mathrm{B}}=\) \(-2.0 \mu \mathrm{C}, q_{\mathrm{c}}=+5.0 \mu \mathrm{C},\) and \(q_{\mathrm{D}}=+12.0 \mu \mathrm{C}\) (a) Two of the spheres are brought together so they touch, and then they are separated. Which spheres are they, if the final charge on each one is \(+5.0 \mu \mathrm{C} ?\) (b) In a similar manner, which three spheres are brought together and then separated, if the final charge on each of the three is \(+3.0 \mu \mathrm{C} ?\) (c) The final charge on each of the three separated spheres in part (b) is \(+3.0 \mu \mathrm{C} .\) How many electrons would have to be added to one of these spheres to make it electrically neutral?

Suppose you want to determine the electric field in a certain region of space. You have a small object of known charge and an instrument that measures the magnitude and direction of the force exerted on the object by the electric field. (a) The object has a charge of \(+20.0 \mu \mathrm{C}\) and the instrument indicates that the electric force exerted on it is \(40.0 \mu \mathrm{N}\), due east. What are the magnitude and direction of the electric field? (b) What are the magnitude and direction of the electric field if the object has a charge of \(-10.0 \mu \mathrm{C}\) and the instrument indicates that the force is \(20.0 \mu \mathrm{N},\) due west?

Two very small spheres are initially neutral and separated by a distance of \(0.50 \mathrm{m} .\) Suppose that \(3.0 \times 10^{13}\) electrons are removed from one sphere and placed on the other. (a) What is the magnitude of the electrostatic force that acts on each sphere? (b) Is the force attractive or repulsive? Why?

A charge \(+q\) is located at the origin, while an identical charge is located on the \(x\) axis at \(x=+0.50 \mathrm{m} .\) A third charge of \(+2 q\) is located on the \(x\) axis at such a place that the net electrostatic force on the charge at the origin doubles, its direction remaining unchanged. Where should the third charge be located?

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