Physical Science / Unit 10: Electricity and Magnetism
10.2 Current, Voltage and Resistance
Notes
- Current (I) is the flow of charge, measured in amperes (A).
- Voltage (V) is the energy given to each unit of charge, measured in volts (V); it is the push that drives current. Batteries and generators are voltage sources.
- Resistance (R) opposes current, measured in ohms ($\Omega$). Longer, thinner and hotter wires have more resistance.
- A circuit is a closed loop. If it is broken (open), current stops. A switch opens and closes a circuit.
- Direct current (DC) flows one way (batteries). Alternating current (AC) reverses direction (wall outlets).
Practice
What is the unit of electric current?
Current is measured in amperes.
What happens to current if a switch in a simple circuit is opened?
An open switch breaks the closed loop.
Which wire has the least resistance?
Shorter and thicker wires resist current less.
Ready for more? Take the Unit 10 test.