Electric Charge Key Question How do electric charges

Electric Charge Key Question: How do electric charges interact?

Electric forces § Electric forces are created between all electric charges. § Because there are two kinds of charge (positive and negative) the electrical force between charges can attract or repel.

Electric forces § The forces between the two kinds of charge can be observed with an electroscope.

Electric forces § Charge can be transferred by conduction.

Electric current § The direction of current was historically defined as the direction that positive charges move. § Both positive and negative charges can carry current. § In conductive liquids (salt water) both positive and negative charges carry current. § In solid metal conductors, only the electrons can move, so current is carried by the flow of negative electrons.

Fields and forces § The concept of a field is used to describe any quantity that has a value for all points in space. § You can think of the field as the way forces are transmitted between objects. § Charge creates an electric field that creates forces on other charges.

Fields and forces § Mass creates a gravitational field that exerts forces on other masses.

Fields and forces § Gravitational forces are far weaker than electric forces.

21. 2 Drawing the electric field

21. 2 Electric fields and electric force § On the Earth’s surface, the gravitational field creates 9. 8 N of force on each kilogram of mass. § With gravity, the strength of the field is in newtons per kilogram (N/kg) because the field describes the amount of force per kilogram of mass.

21. 2 Electric fields and electric force § With the electric field, the strength is in newtons per coulomb (N/C). § The electric field describes the amount of force per coulomb of charge.