# If the lights turn off it means that the bulbs are

• Notes
• apiccirello
• 25

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If the lights turn off, it means that the bulbs are wired in series. The other situation would be if the remaining lights stayed on, then it would be parallel.

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Page | 22 Parallel Circuit Problem Solving 1. A parallel circuit contains a 12-V battery and three bulbs with a resistance of 4 Ω, 6 Ω, and 8 Ω. What is the total resistance in the circuit? What is the voltage drop of each bulb? What is the current that each bulb uses? What is the power in each bulb? Resistance (Ohms) Current (Amps) Voltage (Volts) Power (Watts) Bulb 1 4 Ω 3 A 12 V 36 W Bulb 2 6 Ω 2 A 12 V 24 W Bulb 3 8 Ω 1.5 A 12 V 18 W Total 1.85 Ω 6.5 A 12 V 78 W 2. A parallel circuit contains a 120-V battery and three bulbs with a resistance of 20 Ω, 30 Ω, and 60 Ω. What is the total resistance in the circuit? What is the voltage drop of each bulb? What is the current that each bulb uses? What is the power in each bulb? Resistance (Ohms) Current (Amps) Voltage (Volts) Power (Watts) Bulb 1 20 Ω 6 A 120 V 720 W Bulb 2 30 Ω 4 A 120 V 480 W Bulb 3 60 Ω 2 A 120 V 240 W Total 10 Ω 12 A 120 V 1,440 W 3. A parallel circuit contains a 6-V battery and three bulbs with a resistance of 2 Ω, 4 Ω, and 8 Ω. What is the total resistance in the circuit? What is the voltage drop of each bulb? What is the current that each bulb uses? What is the power in each bulb? Resistance (Ohms) Current (Amps) Voltage (Volts) Power (Watts) Bulb 1 2 Ω 3 A 6 V 18 W Bulb 2 4 Ω 1.5 A 6 V 9 W Bulb 3 8 Ω 0.75 A 6 V 4.5 W Total 1.14 Ω 5.25 A 6 V 31.5 W
Page | 23 Parallel Circuit Homework 1. A parallel circuit contains a 20-V battery and three bulbs with a resistance of 2 Ω, 4 Ω, and 6 Ω. What is the total resistance in the circuit? What is the voltage drop of each bulb? What is the current that each bulb uses? What is the power in each bulb? Resistance (Ohms) Current (Amps) Voltage (Volts) Power (Watts) Bulb 1 2 Ω 10 A 20 V 200 W Bulb 2 4 Ω 5 A 20 V 100 W Bulb 3 6 Ω 3.33 A 20 V 66.6 W Total 1.09 Ω 18.33 A 20 V 366.6 W 2. A parallel circuit contains a 60-V battery and three bulbs with a resistance of 5 Ω, 10 Ω, and 15 Ω. What is the total resistance in the circuit? What is the voltage drop of each bulb? What is the current that each bulb uses? What is the power in each bulb? Resistance (Ohms) Current (Amps) Voltage (Volts) Power (Watts) Bulb 1 5 Ω 12 A 60 V 720 W Bulb 2 10 Ω 6 A 60 V 360 W Bulb 3 15 Ω 4 A 60 V 240 W Total 2.73 Ω 22 A 60 V 1,320 W

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Page | 24 The Tollway Analogy The flow of charge through the wires of a circuit can be compared to the flow of cars along a toll way system in a very crowded metropolitan area. The main source of resistance on a toll way system are the tollbooths. Stopping cars and forcing them to pay a toll at a tollbooth not only slows the cars down, but in a highly trafficked area, will also cause a bottleneck with a backup for miles. The rate at which cars flow past a point on that toll way system is reduced significantly by the presence of a tollbooth. Clearly, tollbooths are the main resistor to car flow. This can also be related to thinking about walking through the hallways at school. If there were multiple pathways to walk down, then it would be much easier to walk to the front office. If the class were restricted to only one hallway for the trip, then it would take longer and would be more crowded with people pushing their way through.
• Fall '12
• Beatty
• Charge, Current, Resistor, Electrical resistance, Series and parallel circuits, Bulb

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