Name __________________________________
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________________________
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.
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Activities 1 and 2 - Page 1/1
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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.
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Activity 3 - Page 1/1
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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?
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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.
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Activity 6 - Page 1/1
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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
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Activity 7 - Page 1/3
Name __________________________________
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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!
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Activity 7 - Page 2/3
Name __________________________________
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________________________
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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?
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Activity 7 - Page 3/3