Electricity
This unit on electricity will be an interactive unit. You will need to go to the link below to complete your activities:
http://www.stmary.ws/HighSchool/Physics/home/notes/electricity/circuits/default.htm
Activity 1: Nikola Tesla:
1. Scroll down on the page (follow the link above) and watch “The Genius of Nikola Tesla”
2. Investigate the 3 major contributions of Nicola Tesla and provide a brief explanation for each and complete
the table below.
Contribution #1
Contribution #2
Contribution #3
Activity 2: Conductivity & the 4th State of Matter
1. Watch the video: Plasma – 4th State of Matter
2. Define Electric Current
3. Compare the conductivity of Solids, Liquids and Gases
Solids
4. Identify 3 things about Plasma
Activity 3: Current
1. Identify 3 conditions for passing a current.
Liquids
Gases
Activity 4: Ohm’s Law
1. Identify and relate the following circuit terms: Electric Charge, Current, Resistance, and Voltage.
Description
Units
Electric Charge
Current
Resistance
Voltage
1. Watch the videos:
o Electric Current
o Resistance in a Wire
o Resistance Model
2. Apply Ohm’s Law to solve electric circuit problems.
I = q/t
R = V/I
3. What causes “Resistance”?
4. What is another name given to Voltage?
Practice Problems
1. If 10. Coulombs of charge are transferred through an electric circuit in 5.0 seconds, then the current in the
circuit is?
2. A wire carries a current of 2.0 amperes. How many electrons pass a given point in this wire in 1.0 sec?
3. How many electrons pass through a circuit in 60 seconds if the resistance is 9.6 Ohms and the voltage is 9?
4. Circle the graph that correctly shows the relationship between Voltage
and Current. Briefly explain your reasoning.
5. What does the lope of the correct graphical relationship between Voltage
and Current reveal?
6. Circle the graph that correctly shows the relationship between Current and
Resistance. Briefly explain your reasoning.
7. A light bulb is plugged into a wall outlet (220 V) and it uses 0.68 Amps. What
is the light bulbs resistance?
8. A flash light bulb is labeled to use 1.77 AMPS and its resistance is 1.60 Ω. What voltage is the light bulb
rated for?
9. A toaster plugged into the wall, (120 volts), uses 14 Amps of electricity. What is the resistance of the
toaster?
10. The resistance of dry human skin is about 500,000 Ω and wet, sweaty, human skin is about 1000 Ω. How
much current passes across someone’s fingers if they touch the leads of a 9 volt battery when their skin is
wet and dry?
Activity 5: Resistance in a Wire
1. Watch the video “How a light bulb works” explain how a light bulb works.
2. Identify the 3 factors that affect resistance.
3. Briefly explain why powerful speakers require thick speaker wires.
4. Using the equation that relates Resistivity, Length of a wire and cross section (diameter) of a wire. Circle the
correct graphical relationship between Resistance and Diameter of a wire.
R = ρL/A
5. Circle which wire has the least resistance.
6. Play the “Resistance and Wires” interactive game
until you get two successful outcomes.
7. Watch the “Principles of Electricity – Heat Light”
video to answer the following questions:
What makes a material an
insulator?
What are 3 examples of
insulators?
What are 2 things that happen
when electrons collide in a
conducting material?
What are the requirements of
that power plants must meet to
supply the great demand of
energy in our society?
Why your personal computer
has an internal fan built in it?
What makes a material a Super
Conductor?
Activity 6: Brainiac – Electric Fence
1. Watch the “Brainiac – Electric Fence” video and enjoy it!!!
2. What a 3 conclusions that you can make about the electricity example given in the video.
Conclusion #1
Conclusion #2
Conclusion #3
Activity 7: Circuit Concepts
1. Watch the “Temperature and Current - MIT TV” video.
2. Why does the lightbulb get brighter when the rod is placed in the liquid nitrogen?
3. Kirchhoff's 1st Law states that:
4. What does Kirchhoff's 1st Law prove?
5. Identify the following symbols used in circuitry:
OUT
6. Explain if this partial circuit diagram is correct.
IN
7. Kirchhoff's 2nd Law states that:
IN
8. How does Kirchhoff's 2nd Law relate to the Conservation of Energy Law:
Activity 8: Series and Parallel Circuits
1. Watch the “Electricity – Series + Parallel Circuits”
2. Draw a circuit in series with 3 resistors and a parallel circuit with 4 resistors
Series Circuit
Parallel Circuit
3. Analyze and study the notes on Series and Parallel Circuits.
A. Series Circuits: Current (I) the same all over. True for both AC and DC.
1. First find RTotal.
RTotal = R1 + R2 + R 3 + …
I
2. Next find I.
Vs V 1

RT R1
V 1  I  R1
V 2  I  R2
3. Next get V1, V2, etc.
Vs  V 1  V 2  ...
B. Parallel Circuits: Gives several loads the same voltage. Allows some loads to be shut down while others may still
draw current.
1. First get RTotal.
1
1
1


 ...
RT R1 R 2
2. Next get I1 and I2…
Vs
R1
Vs
I2 
R2
3. Next get ITotal.
IT = I1 + I2 + …
I1 
Vs
ITotal
R1  R 2
RT 
for only 2 resistors
R1  R 2
RT 
4. Other helpful formulas:
5. As branches are added, IT increases and RT decreases.
6. Voltage across each branch of a parallel circuit is the same as Vs.
7. The branch with the most R has the least current, and the branch with the least R has the most current.
Activity 9: Distinguish between Series and Parallel Circuits
1. Describe briefly the difference between a circuit in series and a circuit in parallel.
Series Circuit
Parallel Circuit
2. Explain the difference between Direct Current (DC) and Alternating Current (AC). Draw how DC and AC
currents travel through a wire.
DC
AC
Drawing of DC traveling through a wire
Drawing of AC traveling through a wire
3. Which type of circuit is used for Christmas lights and why.
Practice Problems
1. Find the total current and total resistance in the circuit below.
2. Find the missing information in the circuit below as well
as the total resistance in the circuit.
3. Find the total resistance for 3 resistors of 2.0 ohms, 5.0 ohms and 2.0 ohms connected in parallel.
4. For the circuit below find the missing information
and the total resistance of the circuit.
5. Complex or combined circuits use component in series and parallel. Find the total resistance and total
current of the circuit below.
6. Find the total resistance and total current of the circuit below.
7. Find the total resistance and total current of the
circuit below.