This type of wiring, often found in older holiday lights, is called a series circuit . A circuit that has more than one pathway for electrons to follow is called a parallel circuit . An electric breaker or fuse acts like an emergency switch that shuts the power off when too much current is flowing. Resistance is a factor that opposes the flow of electricity. A good conductor of electricity, such as copper, has low resistance.
Electrical resistance is measured in units called ohms .
V stands for voltage. R stands for resistance. While a capital I is the symbol for current, the actual units that current is measured in are called amperes , or amps for short.