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Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ QUESTIONS AND CALCULATIONS DIRECTIONS FOR ALL ACTIVITY CALCULATIONS–SHOW YOUR WORK AS FOLLOWS: 1. Start by writing the short formula (for example, V = I x R ). 2. Next, rewrite it substituting any values given in the problems for their abbreviated letters. 3. Remember to include the correct unit after your number in your boxed answer. SCHEMATIC DIAGRAM OF SERIES CIRCUIT SERIES CIRCUIT ACTIVITY 1 – OHM’S LAW Calculate the resistance of your circuit in ohms (Ω) given that the current running through this circuit is 0.5 amperes (0.5 A) and that you are using a 6-volt battery. ACTIVITY 2 – OPEN AND CLOSED CIRCUITS Given a 1.5-volt battery and 0.5-ohm lightbulb, calculate the current of your circuit in amps. Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activities 1 and 2 - Page 1/1 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ ACTIVITY 3 – SERIES CIRCUIT QUESTIONS SERIES CIRCUIT 1. What happened to the brightness of the bulbs each time you added a new bulb wired in series? a. They got brighter. b. They got dimmer. c. They stayed the same. 2. How did adding a second battery in series affect the brightness of the bulbs? a. They got brighter. b. They got dimmer. c. They stayed the same. ACTIVITY 3 – PARALLEL CIRCUIT QUESTIONS PARALLEL CIRCUIT 1. What happened to the brightness of the bulbs each time you added a new, similar bulb wired in parallel? a. They got brighter. b. They got dimmer. c. They stayed the same. 2. What happened to the brightness of the bulbs when you added a new, similar battery in parallel with the first one? a. They got brighter. b. They got dimmer. c. They stayed the same. Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 3 - Page 1/1 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ ACTIVITY 5 – POWER AND ENERGY CALCULATIONS Calculate Your Power Use and Electric Bill for a Single Light 1. Remember that Power = Current x Voltage or P = I V , so start by finding out what these values are. First, use a form of Ohm's law (I = V / R ) to calculate the current, using a voltage of 120 V and a lightbulb resistance of 240 ohms. What is the current in amps? 2. Power is calculated in watts, but we're charged for kilowatt·hours (energy used), so you'll have to convert the watts to kilowatts by multiplying by this fraction, which equals 1 (since 1 kW = 1,000 W): 1 kW / 1,000 W. a. How many kilowatts of power does this circuit use? b. If you run the circuit for 30 minutes, how many kilowatt·hours (kWh) of energy will the circuit use? Remember to convert the time from minutes to hours by multiplying by this fraction, which equals 1 (since 1 hour = 60 min): 1 h / 60 min. c. If electricity costs $0.08 per kWh, what will the power company charge to run this circuit for 30 minutes, seven days a week, for a 30-day month? Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 5 - Page 1/1 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ ACTIVITY 6 – SERIES CIRCUIT CALCULATIONS SERIES CIRCUIT Observation: How is current affected by adding lightbulbs? a. The amount of current stays the same when bulbs are added. b. The amount of current gets larger as each bulb is added. c. The amount of current gets smaller as each bulb is added. Calculations For the series circuit pictured, the three lightbulb loads are identical. The battery source is 6 volts ( VT = 6 volts). The total resistance ( RT ) is 1.5 ohms. 1. Calculate the total current ( IT ), which is the same as the individual currents. 2. Calculate the resistance of the individual bulbs ( R1, R2, and R3 ) for this series circuit. Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 6 - Page 1/1 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ ACTIVITY 7 – PARALLEL CIRCUIT CALCULATIONS Observation: How is current (the rate of electron flow) through each circuit path affected by adding lightbulbs in parallel? a. The amount of current stays the same when bulbs are added. b. The amount of current gets larger as each bulb is added. c. The amount of current gets smaller as each bulb is added. PARALLEL CIRCUIT Sample Calculation You have a dry cell with a voltage of 6 volts (VT) connected to three lightbulbs wired in parallel to each other. The three bulbs have resistances of 400, 500, and 600 ohms (R1, R2, and R3), respectively. This is how to complete the calculations: 1. Total resistance (RT), calculated using the reciprocal formula 1 -----------------1 1 1 --- + --- + --R1 R2 R3 RT = RT = RT = 1 ----------------------------------------------0.0025 Ω + 0.0020 Ω + 0.0017 Ω RT = 1 ------------0.0062 Ω RT = 161 Ω 1 -------------------------1 1 1 ------ + ------- + ------400 Ω 500 Ω 600 Ω Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 7 - Page 1/3 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ Activity 7 – Parallel Circuit Calculations – Sample Calculation (continued) You have a dry cell with a voltage of 6 volts (VT) connected to three lightbulbs wired in parallel to each other. The three bulbs have resistances of 400, 500, and 600 ohms (R1, R2, and R3), respectively. This is how to complete the calculations: 2. Individual currents (I1, I2, and I3) Remember, the total voltage (VT), which is the voltage of the source dry cell, equals the voltage for each path. In other words, VT = V1 = V2 = V3. I1 = V1 / R1 I1 = 6 V / 400 Ω I1 = 0.015 A (or 15 mA) I2 = V2 / R2 I2 = 6 V / 500 Ω I2 = 0.012 A (or 12 mA) I3 = V3 / R3 I3 = 6 V / 600 Ω I3 = 0.010 A (or 10 mA) 3. Total current, IT (using the sum of the individual currents) IT = I1 + I2 + I3 IT = 0.015 A + 0.012 A + 0.010 A IT = 0.037 A 4. Total current (using Ohm's law) IT = VT / RT IT = 6 V / 161 Ω IT = 0.037 A (or 37 mA) 5. Is total current the same using both methods of calculation? Yes, IT = 0.037 A using both methods of calculation! Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 7 - Page 2/3 Name __________________________________ Date ________________________ Teacher ________________________________ Period ________________________ Parallel Circuit Calculations Given a battery voltage of 3 V and lightbulbs with individual resistances of 2, 3, and 4 ohms, solve for the following values. First, write the short formulas. Next, substitute known values for the letter abbreviations. Remember to show the units after all the numbers. Do the math. 1. The voltages across each lightbulb, V1, V2, and V3. V1 V2 V3 2. The total resistance, RT. 3. The currents in each circuit path, I1, I2, and I3. I1 I2 I3 4. The total current, IT. Do you know how smart you are for being able to solve this problem? Privacy Statement and Copyright © 1999-2004 by Wheeling Jesuit University/the NASA-supported Classroom of the Future program. All rights reserved. Some images copyright © 2004 www.clipart.com. Activity 7 - Page 3/3