Electricity & Magnetism, Chapter 2, Section 1: Electric Charge & Static Electricity
What are the methods of transferring an electric charge?
1) Friction (transfer of electrons from one uncharged object to another uncharged object by rubbing); 2) Conduction (transfer of electrons from a charged object to another by direct contact); and 3) induction (movement of electrons to one part of an object, caused by the electric field of another object).
What is conduction?
A method of charging an object by allowing electrons to flow by direct contact from one object to another object. (the transfer of electrons from a charged object to another object by direct contact)
What is induction? How does it work?
A method of charging an object by means of the electric field of a second (charged) object, without the two objects having any direct contact. The electric field around the charged object attracts or repels electrons in the other object, moving the electrons to one part of the object, causing the object to become charged.
What is friction?
A method of charging an object by rubbing it against another object. (the transfer of electrons from one uncharged object to another by rubbing)
What is an electron?
A negatively charged particle that is found outside the nucleus of an atom.
What is a proton?
A positively charged particle that is part of an atom's nucleus.
How can an object become charged?
An uncharged object becomes charged when electrons are transferred from one location to another. If an object loses electrons, it will have more protons than electrons and will have an overall positive charge; if it gains electrons, it will have more electrons than protons and will have an overall negative charge. The three methods of transferring a charge are friction, conduction, and induction.
How do electric charges interact with each other?
Charges that are the same repel each other. Charges that are different attract each other.
Explain static discharge?
Charges that build up as static electricity don't stay forever. Electrons tend to move, returning the object to its neutral position. For example, when a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. The loss of static electricity as electric charges transfer from one object to another is called "static discharge."
How does charging by conduction work?
Charging by conduction is the transfer of electrons from a charged object to another object by direct contact. Electrons transfer from the object that has the more negative charge to the one that has the more positive charge.
How does charging by friction work?
Charging by friction is the transfer of electrons from one uncharged object to another uncharged object by rubbing. When two uncharged objects rub together, some electrons from one object can move onto the other object. The object that gains electrons becomes negatively charged; the object that loses electrons becomes positively charged.
How can an electric charge be detected?
Electric charge can be detected by an instrument called an electroscope.
What do the lines represent in an electric field diagram?
Electric field lines represent the electric field and are drawn with arrows to show the direction of the electric force. A negative charge points inward; a positive charge points outward. The strength of an electric field is represented by how close the electric field lines are to each other. The greater the distance between the lines, the weaker the electric field is.
What happens when negatively and positively charged objects are brought together?
Electrons transfer until both objects have the same charge.
How does lightening work?
Lightening is a dramatic example of static discharge. During thunderstorms, water droplets within clouds become charged. To restore a neutral condition in the clouds, electrons move from areas of negative charge to areas of positive charge and produce an intense spark, which is lightening.
What role does induction play when lightening strikes Earth?
Some lightening reaches Earth because negative charges at the bottom of storm clouds may cause the surface of Earth to become positively charged by induction. Electrons jump between the cloud and Earth's surface, producing a giant spark as they travel through the air.
Who came up with the names for electric charges?
The American inventor, Benjamin Franklin gave charges the names "positive" and "negative" in the 1700s.
What is an electric force?
The attraction or repulsion between electric charges.
What is static electricity?
The buildup of charges on an object. Charges build up on the object but do not flow continuously.
What is conservation of charge?
The law that states that charges are neither created nor destroyed but only transferred from one material to another.
What is an electric field?
The region around a charged object where the object's electric force interacts with other charged objects.
What is a neutron?
The small uncharged particle that is found in the nucleus of an atom.
How does an electroscope work?
When the electroscope is uncharged, its metal leaves hang straight down. When a charged object touches the knob, electric charge travels by conduction into or out of the leaves. Since the charge on both leaves is the same, the leaves repel each other and spread apart.
What are the two types of electric charge?
positive and negative
