CircuitCircuit complete (closed) path along which a charge may flow similar to a closed set of pipes with H2O Battery acts as a pump
2 Basic Types of Circuits1.Series Circuits Everything is lined up in a row current goes through a single path current is resisted by each individual device What happens if one device fails?
2. Parallel Circuits Everything is lined up separately Voltage is the same across each device Current divides among the branches
Circuit Diagramming Shorthand method of drawing circuits • Must use symbols. • Wires are drawn in straight lines. • Wires meet at 90° angles.
Measuring Voltage and CurrentWhen measuring voltage, the volt meter needs to be hooked in parallel to the circuit. R2 R3 R4 R1
Measuring Voltage and CurrentWhen measuring amperage, the am meter needs to be hooked in series to the circuit. R1 R2 R3
Overloading too much current is drawn out causing the wires to heat up Only happens in parallel circuits Use Fuses or Circuit Breakers Electromagnets that open a switch interrupting the flow of Piece of metal that current melts at a certain current opening the circuit
• To find resistance of a circuit with resistors in series just add all the resistors. R1 + R2 + Rx …. = Requivalent• Example: three resistors of values 30 ohm, 40 ohm, and 50 ohm are connected in series to a 12 V battery. What is the equivalent resistance? Circuit Current?• 30 + 40 + 50 = 120 Ohm• Use the Requivalent , the given voltage, and Ohm’s Law to find the current through the whole circuit.• V = IR 12 = I x 120 12/120 = .1 Amps• Use V = IR to find the voltage through each resistor.• V1 = .1(30) V2 = .1(40) V3 = .1(50)• Add all the voltages 3 + 4 + 5 = 12 V (original)
• To find equivalent resistance of resistors in parallel add the inverses of each resistor and take the inverse of the answer.• 1/R1 + 1/R2 + 1/Rx… = 1/Requivalent• Example: Three resistors are connected in parallel to a 12 Volt battery as follows, 30 Ohm, 40 Ohm, and 50 Ohm. Find the equivalent resistance and the current through the circuit.• Use x-1 on your calculator.• 1/30 + 1/40 + 1/50 = 1/R 1/R = 12.76 Ohms• V = IR to find current through circuit• 12 = I(12.76) 12/12.76 = .94 Amps• Use V = IR to find current through each resistor• 12 = I(30) 12 = I(40) 12 = I(50)• .4 + .3 + .24 = .94 Amps
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