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Type:
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Description:
Duration:
Author(s):
Graduated Difficulty
Lesson Plan
Physical Science
8
Students will practice calculating resistance, current, and voltage of
electric currents.
45+ Minutes
Rossie Kennedy
Instructional Unit Content
Standard(s)/Element(s)
Content Area Standard
S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as
major kinds of forces acting in nature.
c. Investigate and explain that electric currents and magnets can exert force on each other.
TAG Standard
Higher Order and Critical Thinking Skills
4. Make and evaluate decisions using criteria
Summary/Overview
The focus of this lesson is to give students the opportunity to assess their own understanding
of how to compute electrical current, resistance, and voltage. Students will also make
decisions about what they need to do to improve their understanding/skill.
Enduring Understanding(s)
At the end of this lesson the student will understand that
a. Ohm’s Law shows how current, resistance, and voltage are all related.
Essential Question(s)
How do you solve problems using Ohm’s Law? How do changes in current, resistance, and
voltage affect each other?
1
Concept(s) to Maintain
Ohm’s Law describes how electrical currents, voltage, and resistance are all related. The
equation can be algebraically manipulated to solve for any of the missing variables.
Evidence of Learning
What students should know:
 electric current - flow of charge through a conductor - unit is amperes (A)
[reminder… in solids, electrons flow - in liquids/gases, ions flow]
 voltage - how much electric energy a battery can pass on to electrons in a circuit - unit
is volts (V)
 resistance - how difficult it is for electrons to flow - unit is ohms (Ω) - longer,
thinner wires have higher resistance - insulators have much higher resistance than
conductors
 Ohm’s Law
current = voltage/resistance
I=
𝑉
𝑅
 ↑ voltage = ↑ current…..directly proportional
↑ resistance = ↓ current……inversely proportional
What students should be able to do:
a. Algebraically rearrange Ohm’s Law equation to solve for any of the missing
variables.
b. Mathematically show how changes in electrical current, voltage, and resistance affect
each other.
c. Make and evaluate decisions using criteria.
Suggested Vocabulary
Ohm’s Law, current, resistance, voltage
Procedure(s)
Phase 1: Hook
1.
Discussion: Do your individual actions affect other people that you are in relationship with?
Give an example.
If two things are in relationship to one another and one changes, how will it affect the other?
2
Phase 2: Acquiring Content
2.
Present Ohm’s Triangle to explain how voltage, current, and resistance are related. Do sample
calculations and demonstrate how to algebraically rearrange equations to solve for different
variables.
Phase 3: DECIDE and Practice and DECIDE
3.
Explain “You will now be given an opportunity to practice what you have learned. Because
everyone learns at a different pace, I will leave it up to you to decide which problem set is most
appropriate for you. To help you make the best choice let’s consider a few questions.”
Distribute the DECIDE handout and three problem sets. Provide time for students to
examine the three sets and decide which is the most appropriate challenge to complete..
5. Students will complete the problem set of their choice and check their work. Students
who quickly and accurately complete their selected set should try the next level.
Students who quickly and accurately complete Level C should create a more difficult
Level D with a corresponding answer sheet. They can trade problem sets with other
Level D students.
6. When all students have had an opportunity to complete and check at least one problem
set, lead the students in a discussion to identify the criteria they used to make their
choice, determine if the first choice was the best choice, and determine the
knowledge/skills needed to move to the next level.
7. Each student will establish a learning goal to improve their own achievement related to
understanding and using the order of operations.
4.
Summarizing Activity

Sum It Up!: Create the most complex electrical calculation that you can think of.
Work the problem. What answer might someone get if s/he did not know Ohm’s
Law or understand the relationship between current, voltage, and resistance?

Resource(s)
Anchor Text(s):
Holt Science and Technology- Physical Science Textbook
Technology:
Power point: Ohm’s Law
Handouts:
Handout 1:
Handout 2:
Handout 3:
Handout 4:
DECIDE
Level A Problem Set
Level B Problem Set
Level C Problem Set
3
Level A Problem Set
Ohm’s Law and Power Equation Practice Worksheet
Voltage=Current x Resistance
Show all four steps for each problem
STEP1 - RECORD INFO
STEP 2 - WRITE EQUATION
STEP 3 - SUBSTITUTE IN THE EQUATION
STEP 4 – SOLVE
𝑉𝑜𝑙𝑡𝑎𝑔𝑒
Current= 𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑐𝑒
𝑉𝑜𝑙𝑡𝑎𝑔𝑒
Resistance= 𝐶𝑢𝑟𝑟𝑒𝑛𝑡
1. A walkman uses a standard 1.5 V battery. How much resistance is in the
circuit if it uses a current of 0.01 A?
Voltage=1.5 volts
Current=0.01 amperes
Resistance= ?
Resistance=1.5 volts / 0.01 amperes
Resistance=?
2. What current flows through a hair dryer plugged into a 110 Volt circuit if it
has a resistance of 25 ohms?
3. A 12 Volt car battery pushes charge through the headlight circuit resistance of
10 ohms. How much current is passing through the circuit?
4. An electric heater works by passing a current of 100 A though a coiled metal
wire, making it red hot. If the resistance of the wire is 1.1 ohms, what voltage
must be applied to it?
5. A subwoofer needs a household voltage of 110 V to push a current of 5.5 A
through its circuit. What is the resistance of the subwoofer?
4
V=I x R
Problem Set B
𝑉
I= 𝑅
R=
1.
Find the current through a 12-ohm resistive circuit when 24 volts is applied.
2.
Find the resistance of a circuit that draws 0.06 amperes with 12 volts applied.
3.
Find the applied voltage of a circuit that draws 0.2 amperes through a 4800-ohm resistance.
𝑉
𝐼
4. Find the applied voltage of a telephone circuit that draws 0.017amperes through a resistance of 15,000
ohms.
5. A 20-volt relay has a coil resistance of 200 ohms. How much current does it draw?
6. A series circuit has 1200-ohms of total resistance with 12 V as the power supply.
What is the total current of this circuit?
7. What is the increase of current when 15 V is applied to 10000-ohm. rheostat, which is adjusted to
1000-ohm value?
8. A transformer is connected to 120 volts. Find the current if the resistance is 480-ohms?
9. A resistive load of 600-ohms is connected to a 24 V power supply. Find the current through the
resistor.
10. A circuit consists of a 12 V battery connected across a single resistor. If the current in the circuit is
3 A, calculate the size of the resistor.
11. If a small appliance is rated at a current of 10 amps and a voltage of 120 volts, the power
rating would be ______ Watts. (P = I V )
5
V=I x R
Problem Set C – 2 step equations
(substitute in equations to solve for the missing variable)
P= V x I
1. If a blender is plugged into a 110 V outlet that has a resistor size of 37.2 ohms, what amount of power is
used by the blender?
I=V/R therefore P=V x (V/R)
2. If a clock expends 2 W of power from a 1.5 V battery, what amount of resistance is in the clock?
3. Tommy runs his juicer every morning. The juicer uses 90 W of Power and the current supplied is 4.5 A.
How many volts are necessary to run the juicer?
4. Amanda’s hair dryer requires 11A of current and has a resistance of 20 ohms. How much power does it
use?
5. A DC electric motor transforms 1.50 kW of electrical power into mechanical form. If the
motor's operating voltage is 300 volts, how much current does it "draw" when operating at full
load (full power output)?
Challenge
Calculate the amount of power dissipated by this electric heating element, if the generator's
output voltage is 110 volts and the heater's resistance is 2.5 ohms: ( P = V 2/ R )
Now, calculate the power dissipated by the same heater if the generator's output voltage is
doubled.
6