Electricity Electric Current

Electric Current The flow of charges through a wire or conductor is called an electric current

Electric Current Current is the flow of electrons (e-) Current (I) is measured in amperes (A)

Electric Current Charges flow from high voltage to low voltage A voltage difference is the push that causes charges to move Voltage difference is measured in volts (V)

Electric Current For charges to flow, the wire must always be connected in a closed path, or circuit

Sources of Electricity Dry cell battery - produces a voltage difference between its zinc container and carbon rod, causing current to flow between them Wet cell battery - contains two connected plates made of different metals in a conducting solution Wall sockets - a voltage difference across the two holes of an electrical outlet provided by a generator at a power plant

Resistance The tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light All materials have some electrical resistance

Resistance Resistance (R) is measured in ohms (Ω) Making wires thinner, longer, or hotter increases their resistance

The current in a circuit equals the voltage difference divided by the resistance

Applying Ohm’s Law

1.3

1.3 1.3W 3.9V 3.9

Practice Problem

Practice Problem V I R I = V / R I = 1.5V / 2W I = 0.75A