ELECTRIC CURRENTS WHAT IS ELECTRIC CURRENT An electric

ELECTRIC CURRENTS

WHAT IS ELECTRIC CURRENT? � An electric circuit has a source of electric power that has a positive and negative terminal. � Wires are made of electric conductors (often copper wire is used as the conductor) that allow electrons to move easily from one place to another. � The electric current is a measurement of the number of electrons that flow past a point in the circuit.

THE UNIT OF ELECTRIC CURRENT � Electric current is measured in amperes. � The symbol of the ampere is A. � The current can be determined by measuring the amount of charge that passes a point in a certain amount of time. � Current = Charge/Time

TYPES OF ELECTRIC CURRENT � There are two different types of electric current: � Direct Current (DC) � Alternating Current (AC)

DIRECT CURRENT � Direct electric current has the electrons always flowing in the same direction. � Batteries all produce a direct current. � One terminal of the battery is always the positive terminal and the other terminal is always the negative terminal.

ALTERNATING CURRENT � Alternating current has the electrons flowing in one direction at one time and then the current flow is reversed and the electrons move in the opposite direction. � Generators usually provide alternating current. � There are ways to convert from one form of current to another.

MEASURING ELECTRIC CURRENT � Electric Current is measured with an ammeter. � An ammeter must be placed in series with a device that uses electric energy. � An example of a device that uses electric energy is a light bulb.

DIRECTION OF ELECTRIC CURRENT � Electric current was measured before scientists understood that it was the negatively charged electrons that move the current around an electric circuit. � Conventional Current in a DC circuit is shown going from the positive terminal to the negative terminal of a battery or power source. It is represented by the letter I. � Electron Flow in a DC circuit shows the direction of the electrons flowing. It is represented by e-

CONNECTING AN AMMETER � Ammeters must be connected in series in a circuit. � The positive or red terminal is connected closer to the positive terminal of the battery. � The negative or black terminal is connected closer to the negative terminal of the battery.

Digital Ammeter Negative Terminal Positive Terminal

ANALOG AMMETER

ANALOG AMMETER

Selecting Switch Positive Terminal for Current Negative Terminal