Many people were aware of the force before electricity.
The Greeks, Egyptians, and Romans reported on electricity.
English scientist William Gilbert made a study of electricity and magnetism in the 16th century.
Ben Franklin is known for his metal key and kite experiment in a storm.
The 19th century saw real progress with electricity and magnetism.
James Clerk was able to link them together into something called electromagnetism.
The components of atoms are protons, neutrons, and electrons.
The nucleus is made up of protons and neutrons, while electrons swarm around it.
The electrons would be 5 meters away if a nucleus was the size of the period at the end of this sentence.
The electric charge of electrons and protons gives them an attractive force.
Positive and negative electric charge can be found.
Positive and negative particles repel each other.
electrons are negatively charged
Bulk matter is not charged with protons and electrons.
This is because the amount of charge on a protons balances the charge on an electron, which is quite remarkable in light of the fact that protons and electrons are very different particles.
The electric charge of most atoms is zero because the negative charges cancel out the positive charges.
The number of protons and electrons must be balanced in order for matter to be charged.
This can be accomplished by either the removal or addition of electrons.
If you add electrons to the object, it becomes negatively charged.
Charge is conserved.
If you rub a piece of silk on a glass rod, the silk will have a negative charge and the glass will have an equal positive charge.
Net charge can't be created or destroyed.
The magnitude of charge on an electron is referred to as e. The basic unit of electric charge is what this stands for.
The charge of an ionized atom must be a whole number of times.
The charge is quantized for this reason.
The charge of a particle is marked by the letter q to remind us of the quantized nature of electric charge.
Charge is expressed in coulombs in the SI system of units.
A coulomb has about 10 18 electrons.
1.6 x 10 -19 C is the value of e.
The electric force between two charged particles obeys a law that is very similar to the law of gravity.
This is the law of Coulomb's Law.
We think of a negative F E as an attraction between the charges and a positive F E as a repulsion.
The material between the charged particles affects the value of the proportionality constant.
The charge of the protons is + e. The electron has a mass of 9.1 x 10 -31 kg and a charge of e.
Since one charge is positive and the other is negative, the force is one of attraction, which we naturally expect since one charge is positive and the other is negative.
The line that joins the charges is the force between the electron and protons.
Two forces form an action/reaction pair.
The electric force is compared to the gravitational force.
In problems where we calculate electrostatic forces, we neglect gravitational forces.
Three point charges are q 1, q 2 and q 3.
Four equal, positive point charges are located at the edge of a square.
There is a negative point charge placed at the square's center.
The distances between the positive and negative charges are the same and the attractive forces on each diagonal are canceled out.
The net force on the center charge is zero.
Each side of the square has a positive charge and a negative charge.
The diagram on the left shows the components of F 1 and F 2 making right triangles with legs each of 2 cm.
The net electric force on the negative charge is F 1 y + F 2 y, where F is the strength of the force between the negative charge and each of the positive charges.
The center of the line that joins the two positive charges is the direction of the net force.
Two pith balls of mass m are given a charge of + q.
As a result of their electrical repulsion, they are hung side-by-side from two threads.
The net force feels zero when the balls are in equilibrium.
The second equation is divided by the first.
The presence of a massive body such as the Earth causes objects to experience a force directed toward the Earth's center.
The force varies with the square of the distance and the mass of the source.
The space surrounding the Earth is made up of a field created by the Earth.
Any mass placed in this field will experience a force due to the interaction with this field.
The electric force is described using the same process.
The presence of a charge creates an electric field in the space that surrounds it, rather than having two charges reach out across empty space to each other to produce a force.
A force will be experienced by another charge placed in the field.
Assume that a point charge Q in a fixed position is positive.
Imagine moving a positive test charge around to different locations.
The force that the test charge experiences should be called F on q at each location.
The test charge is the reason for dividing.
Each of the forces F we'd measure would be twice as much if we were to use a different test charge.
The factors of 2 would cancel when we divided the force by the test charge, leaving the ratio the same as before.
The ratio tells us if the field is strong because of the source charge, or if it is weak because of the test charge.
The electric field would point away from the source charge if the test charge was positive.
If the source charge is positive, the electric field vectors point away from it; if the source charge is negative, they point toward it.
The electric field decreases as we get farther away from the charge.
The electric field is shorter farther from the source charge.
The electric field in the space surrounding is for a point charge.
To make it easier to sketch an electric field, lines are drawn through the vectors so that the electric field is always parallel to the line.
Your first thought might be that obliterating the individual field vectors deprives us of information, since the length of the field was what told us how strong the field was.
The strength of the field can be figured out by looking at the density of the field lines.
The field is stronger where the field lines are closer together.
The electric force and electric fields obey the same properties.
If we had two source charges, their fields would overlap and effectively add, and a third charge wandering by would feel the effect of all three fields.
Add the electric fieldvector due to one of the charges to the electric fieldvector due to the other charge at each position in space.
In the diagram below, E 1 is the electric field at a particular location due to the charge + Q, and E 2 is the electric field at that same location due to the other charge.
The field E total at that location is given by adding these vectors.
The electric field lines can be sketched.
Electric field lines always point away from positive source charges and toward negative ones.
An electric dipole is a pair of equal but opposite charges.
If a positive charge + q were placed in the electric field above, it would experience a force that is related to the field line passing through + q's location.
The electric fields are sketched from the point of view of a positive test charge.
If a negative charge was placed in the electric field, it would experience a force that is related to the direction of the field line.
Finally, notice that electric field lines don't cross.
A charge q is placed at a location with an electric field strength of 400 N/C.
F on q is equivalent to qE in this case.
The two point charges are separated by a distance of 6.0 cm.
Q and Q are the two source charges.
The electric fieldvector due to + Q would point away from + Q and the electric fieldvector due to - Q would point toward Q.
They point in the same direction, so their magnitudes would add.
If a charge q is placed at the midway point described in the previous example, describe the force it would feel.
If E is 0, then F on q is 0.
Uniform electric fields are an important subset of problems.
One way to create a uniform field is to have two large sheets of conducting paper, each holding a small amount of charge Q.
For all practical purposes, the field is uniform if it is near the edges of each sheet.
A uniform field means having a constant force and therefore a constant acceleration, so you can use equations just like you would near the surface of the Earth.
Positive charge is distributed uniformly over a large horizontal plate, which acts as the source of a vertical electric field.
There is an object of mass 5 g above the plate.
The electric force would be repulsive if the object carried a positive charge.
The charge on the object should be q.
There is a uniform electric field of 20 N/C caused by two large charged plates that are 30 cm apart.
The particles don't interact with each other because they are so far apart.
They are released from the rest.
The force will be the same because the electron and protons have the same magnitude.
The electron travels in the opposite direction of the electric field if you want to know the direction.
Although the charges have the same magnitude of force, the electron's mass is 2000 times smaller than the proton's.
Even though the force is the same and the same work is done on both charges, there is a significant difference in final velocities due to the large mass difference.
The solution would be using kinematics.
The same answers would have been obtained by you.
Materials can be categorized into broad categories based on their ability to allow charge.
If electrons were placed on a metal sphere, they would quickly spread out and cover the outside of the sphere uniformly.
The electrons would be free to move as far away from each other as they could.
conductors conduct electricity and permit the flow of excess charge.
The best examples of conductors are metals.
Aqueous solutions with dissolved electrolytes are conductors.
Electricity is generated because metals bind all but their outermost electron very tightly.
The electron is free to move.
This creates a sea of electrons.
Extra ones that might be added are guarded by impedances, on the other hand.
The atomic lattice is not free of electrons.
Glass, wood, rubber, and plastic are examples of insulators.
Excess charge stays put if placed on an insulator.
A sphere of copper has a negative charge.
The conductor has no electric field.
Excess electrons that are deposited on the sphere move quickly to the outer surface.
The conductor has an excess charge on the outer surface.
There will be no net electric field within the sphere once the excess electrons establish a uniform distribution on the outer surface.
Since there is no excess charge inside the conductor, there are no excess charges to serve as a source or sink of an electric field line cutting down into the sphere.
There is no field in the conductor's body.
You can protect yourself from electric fields by surrounding yourself with metal.
The electric field in your cage will be zero if charges move around on the outer surface.
For points outside the sphere, it can be shown that the sphere behaves as if it's at its center.
The electric field is always on the surface no matter what shape it is.
The diagram is below.
If we want to change the situation, we should start with a neutral metal sphere and bring a positive charge nearby without touching the original metal sphere.
The far side of the sphere will be charged with a positive charge.
There will be a net attraction between Q and the sphere since the negative charge is closer to Q than the positive charge.
The force of electrical attraction between them will be caused by the separation of charge caused by the presence of Q.
This process can be used to make sure that both spheres are charged in the end.
Imagine two neutrally charged spheres on a stand.
The spheres are arranged in a way that they are in contact with each other.
The attraction was the same when a charge was brought near the side of one of the spheres.
The negative excess charges are on the right sphere and the positive excess charges are on the left sphere.
The two spheres are separated by the external charge.
The negative charge is trapped on the right sphere and the positive charge is trapped on the left sphere because the conductors are no longer in contact.
The net charge is the same between the two spheres.
The atoms that make up the sphere will become polarized because there aren't free electrons that can move to the near side.
Their electrons will feel a tug toward Q, and so will spend more time on the side of the atom closer to Q than on the side opposite Q, causing the atoms to develop a distribution of charge that is more negative on the side nearby Q.
The effect isn't as dramatic as the mass movement of free electrons in the case of a metal sphere, but the polarization is still enough to cause an electrical attraction between the sphere and Q.
If you comb your hair, the comb will pick up extra electrons and make it negatively charged.
The paper will be attracted to the comb if you place the electric field source near little bits of paper.
Intermolecular force is caused by the same phenomenon in which the presence of a charge tends to cause polarization in a nearby collection of charges.
The force between the ion and the atom is attractive if the neutral molecule is away from the negatively charged ion.
Chapter 12 contains solutions.
The three point charges are all positive.
The electric field at Point P would have strength if the negative charge were not present.
A sphere of charge + Q is fixed.
A smaller sphere of charge + q is placed near a larger sphere.
An object of charge + q feels an electric force when placed in an electric field.
A charge of -2 Q is transferred to a metal sphere.
All four charges are located at the corners of the square.
The electric force on each charge is zero.
Justify your answer.
Two charges, + Q and +2 Q, are fixed in place along the y axis of an x-y coordinate system as shown in the figure below.
Charge 1 is at the point and Charge 2 is at the point.
Explain briefly if not.
Explain briefly if not.
The force acting on two point charges is described by Coulomb's Law.
The strategies you used in the chapter can be used to solve these problems.
The electric field is given by E and the electric force is given by E.