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Aim: How can we explain parallel circuits?. Do Now: A series circuit has 3 resistors, 20 Ω , 40 Ω , and 60 Ω . What is the total resistance?. R T = R 1 + R 2 + R 3 R T = 20 Ω + 40 Ω + 60 Ω R T = 120 Ω R T in series is always larger than the largest resistor!.
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Aim: How can we explain parallel circuits? Do Now: A series circuit has 3 resistors, 20 Ω, 40 Ω, and 60 Ω. What is the total resistance? RT = R1 + R2 + R3 RT = 20 Ω + 40 Ω + 60 Ω RT = 120 Ω RT in series is always larger than the largest resistor!
Parallel Circuits • A circuit with 2 or more current loops
Light Bulb Demo If one goes out, the others remain lit
In a parallel circuit… • Voltage is constant • Total current is the sum of the currents through each resistor
And resistance… Straw Demo RT in parallel is always smaller than the smallest resistor!
R1 = 10Ω, R2 = 20Ω, R3 = 30Ω, in parallel with a VT = 100V • Draw this circuit • Calculate the current though each resistor R3 = 30Ω R2 = 20Ω R1 = 10Ω VT = 100V
Draw a parallel circuit with a battery, 3 resistors, an ammeter reading the current through R1 and an ammeter reading the current through R3. R1 = 2Ω, R2 = 4Ω, R3 = 8Ω, and the ammeter for R3 reads 2.5 A. R3 = 8Ω I3 = 2.5A R1 = 2Ω R2 = 4Ω