Comparing electric force and gravitational force (practice) | Khan Academy
Comparing electric force and gravitational force. Google Classroom . Coulomb's Law · Practice: Relationship between electric force, charge, and distance. Given the mathematical representation of Coulomb's Law,, where, describe in words the relationship among electric force, charge, and distance. The electric. Coulomb's law, or Coulomb's inverse-square law, is a law of physics for quantifying the amount . If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different . considered approximately correct, but when the charges are moving more quickly in relation to each other, the full.
When the ground connection is removedthe conductor will have a charge opposite in sign to that of the charged object. An example of induction using a negatively charged object and an initially-uncharged conductor for example, a metal ball on a plastic handle. Electrons on the conductor will be repelled from the area nearest the charged object. The electrons on the conductor want to get as far away from the negatively-charged object as possible, so some of them flow to ground.
This leaves the conductor with a deficit of electrons. The conductor is now positively charged. A practical application involving the transfer of charge is in how laser printers and photocopiers work. This is a good web page that gives a nice description of how a photocopier works: University of Delaware Why is static electricity more apparent in winter?
- Coulomb's law
- Coulomb's Law
- Inverse Square Law
You notice static electricity much more in winter with clothes in a dryer, or taking a sweater off, or getting a shock when you touch something after walking on carpet than in summer because the air is much drier in winter than summer. Dry air is a relatively good electrical insulator, so if something is charged the charge tends to stay. In more humid conditions, such as you find on a typical summer day, water molecules, which are polarized, can quickly remove charge from a charged object. Try this at home See if you can charge something at home using friction.
I got good results by rubbing a Bic pen with a piece of paper towel. To test the charge, you can use a narrow stream of water from a faucet; if the object attracts the stream when it's brought close, you know it's charged.Coulomb's Law, Force Three Charges in a Straight Line
All you need to do is to find something to rub - try anything made out of hard plastic or rubber. You also need to find something to rub the object with - potential candidates are things like paper towel, wool, silk, and saran wrap or other plastic. Coulomb's law The force exerted by one charge q on another charge Q is given by Coulomb's law: Remember that force is a vector, so when more than one charge exerts a force on another charge, the net force on that charge is the vector sum of the individual forces.
Remember, too, that charges of the same sign exert repulsive forces on one another, while charges of opposite sign attract. An example Four charges are arranged in a square with sides of length 2.
The charges in the other two corners are What is the net force exerted on the charge in the top right corner by the other three charges? To solve any problem like this, the simplest thing to do is to draw a good diagram showing the forces acting on the charge. You should also let your diagram handle your signs for you.
Force is a vector, and any time you have a minus sign associated with a vector all it does is tell you about the direction of the vector.
If you have the arrows giving you the direction on your diagram, you can just drop any signs that come out of the equation for Coulomb's law. Consider the forces exerted on the charge in the top right by the other three: You have to be very careful to add these forces as vectors to get the net force. In this problem we can take advantage of the symmetry, and combine the forces from charges 2 and 4 into a force along the diagonal opposite to the force from charge 3 of magnitude When this is combined with the The symmetry here makes things a little easier.
If it wasn't so symmetric, all you'd have to do is split the vectors up in to x and y components, add them to find the x and y components of the net force, and then calculate the magnitude and direction of the net force from the components. Example in the textbook shows this process. The parallel between gravity and electrostatics An electric field describes how an electric charge affects the region around it.
It's a powerful concept, because it allows you to determine ahead of time how a charge will be affected if it is brought into the region. Many people have trouble with the concept of a field, though, because it's something that's hard to get a real feel for. The fact is, though, that you're already familiar with a field.
We've talked about gravity, and we've even used a gravitational field; we just didn't call it a field. When talking about gravity, we got into the probably bad habit of calling g "the acceleration due to gravity". It's more accurate to call g the gravitational field produced by the Earth at the surface of the Earth. If you understand gravity you can understand electric forces and fields because the equations that govern both have the same form.
Electrostatic force is directly related to the charge of each object. So if the charge of one object is doubled, then the force will become two times greater.
If the charge of both of the objects is doubled, then what is the new force?
So if the charge of both objects is doubled, then the force will become four times greater. Alteration in the Distance between Charged Objects 3. If the distance separating the objects is doubled, then what is the new force?
ELECTRIC FORCE AND ELECTRIC CHARGE
The electrostatic force is inversely related to the square of the separation distance. So if d is two times larger, then F is four times smaller - that is, one-fourth the original value. If the distance separating the objects is tripled, then what is the new force? So if d is three times larger, then F is nine times smaller - that is, one-ninth the original value.
Two charged objects have an attractive force of 0. If the distance separating the objects is quadrupled, then what is the new force? If the distance separating the objects is halved, then what is the new force?
So if d is two times smaller, then F is four times larger. If the charge of one of the objects is doubled, and the distance separating the objects is doubled, then what is the new force? The electrostatic force is directly related to the product of the charges and inversely related to the square of the separation distance.