Electricity Electric Current Electric Current The flow of

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 some resistance have electrical

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

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

Applying Ohm’s Law

1. 3

1. 3 W 3. 9 V 1. 3 W 3. 9

Practice Problem

Practice Problem V I R I=V/R I = 1. 5 V / 2 W I = 0. 75 A