ElectricityIt’s Shocking!!

Current Electricity

Current Electricity is a constant flow of electrons through a circuit. There are three main parts to a circuit.

Power SupplyThe power supply provides electrons to flow around a

circuit. There are many types of power supplies…AC power supplies, batteries, and generators. We’ll mostly use batteries. The symbol for a power supply depends on the type, but we’ll use the battery symbol for all our power supplies. The long and short lines always come as a pair, the long side being the positive side and the short side as the negative. The number of pairs represents the number of cells in the battery. The output of a power supply is measured in Volts, or Joules/Coulomb. The equation for finding voltage is

WireWire’s job is to carry the electrons, or current, around the circuit. Wire is always drawn as a straight line. The current is measured in Amperes (or Amps) which is a Coulomb/second. Current is found by taking the charge divided by the time it takes that charge to pass, or

ResistanceResistance in a circuit can be anything from a resistor to an appliance to a house or business….it all depends on the circuit! There are many symbols for resistance, but we will always use the generic resistance symbol. A resistor opposes current. The units of resistance are Ohms, and the symbol is a Greek letter Omega Ω.

Ohm’s LawThe most used equation in current electricity is Ohm’s Law. It relates Voltage (V), Current (I) and Resistance (R).

Types of Circuits•There are three types of circuits: simple, series, and parallel.

Simple CircuitA simple circuit contains a power supply, a single resistor and wire.

Series CircuitA series circuit contains a power supply, wire, and two or more resistors. The resistors are connected by a single wire, one after another. A series circuit has low current, and disconnecting one resistor opens the circuit. The equations governing a series circuit are:

VT = V1 + V2

IT = I1 = I2RT = R1 + R2

Parallel CircuitA parallel circuit is made from a power supply, wire, and two or more resistors connected on both sides. The resistors are side-by-side. A parallel circuit has high current, and each resistor can be disconnected without disconnecting the entire circuit. The equations governing a parallel circuit are:VT = V1 = V2

IT = I1 + I21/RT =1/R1 + 1/R2