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Electric Current Chapter 22-2 What is Electric Current? Flow of electric charge Source of electric energy that can be controlled Solids—flowing charges; electrons Liquids—flowing charges; ions Measured in units of amperes (A) Electric charges will flow continuously only through a closed connecting loop called a circuit. Electric Circuits Simplest electric circuit Battery— source of electrical energy Wire— electric conductor Current will flow in the circuit as long as none of the wires (including filament in bulb) is disconnected or broken. Working circuit Broken circuit Electrons move away from the negative battery terminal toward the positive terminal Voltage Measure of how much electrical potential energy each electron can gain Voltage increases—electric potential energy increases Measured in Volts (V) Batteries Supplies energy to an electric circuit When positive and negative terminals are connected in a circuit, the electric potential energy is increased Supplies energy by converting chemical energy to electric potential energy Alkaline Batteries +/- separated by a moist paste Chemical reactions occur in the paste when a current is added Produces an electric field in circuit Batteries contain only a limited amount of chemicals to produce energy Once original chemicals are used up— ”dead” Resistance Measure of how difficult it is for electrons to flow through material Measured in ohms (Ω) Insulators generally have higher resistance than conductors Thinner wires—higher resistance Longer wires—higher resistance Copper wire—low resistance, good conductor Used in homes because wires do not get hot enough to cause fire