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A charge \(+Q\) is located at the origin, and a charge \(+4 Q\) is at distance \(d\) away on the \(x\) -axis. Where should a third charge, \(q\), be placed, and what should be its sign and magnitude, so that all three charges will be in equilibrium?

Short Answer

Expert verified
The third charge q should be negative and its magnitude depends on the distance from the origin where it would be placed for all the three charges to be in equilibrium. The exact value of the charge and its position would be determined by solving the equations formed using Coulomb's Law and the equilibrium conditions.

Step by step solution

01

Setting up the equations

The net force on each charge is equal to zero for the system to be in equilibrium. So, set up the vector equations for each charge using the principle that the electrostatic force between two charges is given by Coulomb's Law: \( F = k \cdot \frac{{q1 \cdot q2}}{{r^2}} \), where \(F\) is the force between the charges, \(k\) is the Coulomb's constant, \(q1\) and \(q2\) are the amounts of charge, and \(r\) is the distance between the charges.
02

Solve for q

The charge q can be placed on either side of the charge \(+Q\) or \(+4Q\) on x-axis. Let's consider it is on the left side of \(+Q\). Now solve the equations derived from step 1 to find the value of charge q. Remember to consider the direction of the forces and the signs of the charges when setting up the equations.
03

Find the Position of q

Since there is equilibrium in the system, the net force experienced by each charge is zero. Therefore, sum the forces experienced by the third charge q due to charges \(+Q\) and \(+4Q\) and equate it to zero to find the distance of q from the origin.
04

Validate the Solution

Verify the solution by ensuring that the forces experienced by all three charges are indeed zero when you plug in the values of the charges and their positions from the solutions obtained in the previous steps.

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Key Concepts

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

Coulomb's Law
Coulomb's Law is a fundamental principle that describes the force between two stationary point charges. It states that the electrostatic force (F) between two charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them. The formula is given by:
  • \(F = k \cdot \frac{{q1 \cdot q2}}{{r^2}}\)
Here, \(k\) is Coulomb's constant, \(q1\) and \(q2\) are the charges, and \(r\) is the distance between them.

This law helps us understand how objects charged with protons and electrons interact with each other. Positive charges repel other positive charges and attract negative charges. Similarly, negative charges repel other negative charges. The direction of the force is along the line joining the two charges. This principle can be used to determine the force experienced by each charge in an electric field.

In the context of electrostatic equilibrium, as mentioned in the exercise, all charges must balance such that the net force on each charge is zero. This means that every charge should exert an equal and opposite force on the others, resulting in no movement.
Electrostatic Force
The electrostatic force is the force of attraction or repulsion between two charged objects. It is one of the four fundamental forces of nature and is described by Coulomb's Law.
  • This force acts over the space separating the charges, and it relies heavily on the magnitudes of the charges involved and their separation distance.
It's crucial to note that like charges repel each other while unlike charges attract each other.

Understanding this force helps in this exercise as it dictates how the third charge needs to balance forces from both existing charges, \(+Q\) and \(+4Q\).

To be in equilibrium, the net electrostatic force experienced by each charge must be zero:
  • This involves setting the sum of the forces acting on each charge equal to zero, considering their directions.
  • For the third charge \(q\), this involves equating the forces exerted by the charges \(+Q\) and \(+4Q\) to ensure that the net force remains balanced.
Harnessing the characteristics of the electrostatic force allows for the strategic placement of \(q\) to achieve desired balance.
Charge Distribution
Charge distribution involves the arrangement of charges in a system and how they influence one another.

In the scenario of the exercise, we want to place the third charge such that the system reaches electrostatic equilibrium:
  • The position of \(q\) needs to be adjusted relative to \(+Q\) and \(+4Q\).
It plays a crucial role in determining where to place \(q\) so that it creates a balance and ensures that forces on each charge nullify each other.

To achieve equilibrium for the three charges:
  • The charge \(q\)'s distance from \(+Q\) and \(+4Q\) significantly impacts the resulting forces.
  • By considering the sum of forces and their directions, the exact position and magnitude for \(q\) can be determined.
In practical terms, this step includes careful calculations to ensure the electrostatic forces among the charges lead to a stable arrangement, where no charge wants to move.

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Most popular questions from this chapter

A point charge \(q_{1}=-4.00 \mathrm{nC}\) is at the point \(x=0.600 \mathrm{~m}, y=0.800 \mathrm{~m},\) and a second point charge \(q_{2}=+6.00 \mathrm{nC}\) is at the point \(x=0.600 \mathrm{~m}, y=0 .\) Calculate the magnitude and direction of the net electric field at the origin due to these two point charges.

Imagine two \(1.0 \mathrm{~g}\) bags of protons, one at the earth's north pole and the other at the south pole. (a) How many protons are in each bag? (b) Calculate the gravitational attraction and the electric repulsion that each bag exerts on the other. (c) Are the forces in part (b) large enough for you to feel if you were holding one of the bags?

Negative charge \(-Q\) is distributed uniformly around a quarter-circle of radius \(a\) that lies in the first quadrant, with the center of curvature at the origin. Find the \(x\) - and \(y\) -components of the net electric field at the origin.

Two small spheres spaced \(20.0 \mathrm{~cm}\) apart have equal charge. How many excess electrons must be present on each sphere if the magnitude of the force of repulsion between them is \(3.33 \times 10^{-21} \mathrm{~N} ?\)

Two very large parallel sheets are \(5.00 \mathrm{~cm}\) apart. Sheet \(A\) carries a uniform surface charge density of \(-8.80 \mu \mathrm{C} / \mathrm{m}^{2},\) and sheet \(B,\) which is to the right of \(A,\) carries a uniform charge density of \(-11.6 \mu \mathrm{C} / \mathrm{m}^{2} .\) Assume that the sheets are large enough to be treated as infinite. Find the magnitude and direction of the net electric field these sheets produce at a point (a) \(4.00 \mathrm{~cm}\) to the right of sheet \(A ;\) (b) \(4.00 \mathrm{~cm}\) to the left of sheet \(A ;\) (c) \(4.00 \mathrm{~cm}\) to the right of sheet \(B\).

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