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Series and Parallel Circuits Circuits In order for electricity to flow we need Power source Closed circuit There are two type of circuits we will explore Series circuit Parallel circuit Series Circuit In a series circuit there is only one path for the electrons to flow In other words all the components are in series with each other Because there is only one path each charge will go through each resistor Predict, Test and Explain • How will the brightness of the bulbs change as we add more in series? + + + • What does this imply about the current in the circuit? Parallel Circuit In a Parallel circuit there are multiple pathways for charge to flow Each device is placed on it’s own separate branch Current goes through each of the branches at the same time Predict, Test and Explain • How will the brightness of the bulbs change as we add more in parallel? + + + • What does this imply about the current in the circuit? Key Concepts Bulbs in series represent a source of resistance to current flow, similar to boulders in a stream which can block the flow of water Bulbs in parallel offer additional pathways for current flow, similar to branches of a stream which can carry more water. Calculating Resistance in Series Circuits The rule for calculating Series Circuits is to… Add up the values of each individual in the series. R1 + R2 + R3… 5 + 5 + 10 20 Ω (ohms) Calculating Resistance in Series Circuits Add up the values of each individual in the series. R1 + R2 + R3… 10 + 20 + 10 40 Ω (ohms) 10 20 Calculating Resistance in Series Circuits The rule for calculating Series Circuits is to… Add up the values of each individual in the series. 1 1 1 1 -- = -- + -- + - 1 Rt R1 R2 R3 -- = 1 1 1 1 1 Rt -- = -- + -- + -Rt 4 4 2 1 -- = Rt 1 1 -- = .25 + .25 + .5 Rt Rt = 1 Ω (ohms) 1 -- = 1 Rt 1 -- = 1 Rt 20 • • • • • • • Calculating Resistance in Series Circuits The rule for calculating Series Circuits is to… Add up the values of each individual in the series. 1 1 1 1 -- = -- + -- + -• 1 Rt R1 R2 R3 -- = Rt 1 1 1 1 .016 -- = -- + -+ -Rt 100 200 1000 • Rt = 62.5 Ω (ohms) 1 -- = .01 + .005 + .001 Rt 1 -- = .016 Rt 1 -- = .016 Rt 100 200 1000 20