Download Ohm`s Law relates the voltage, current and resistance of a circuit. It

Name: ___________________________
Date: _______________
Block: _______
Virtual Ohm’s Law Lab
Background:
When beginning to explore the world of electricity and electronics, it is vital to start by understanding
the basics of voltage, current, and resistance. These are the three basic building blocks required to
manipulate and utilize electricity. At first, these concepts can be difficult to understand because we
cannot “see” them. One cannot see with the naked eye the energy flowing through a wire or the voltage
of a battery sitting on a table. Even the lightning in the sky, while visible, is not truly the energy
exchange happening from the clouds to the earth, but a reaction in the air to the energy passing through
it.
The three basic principles for a circuit can be explained using electrons, or more specifically, the
charge they create:



Voltage is the difference in charge between two points.
Current is the rate at which charge is flowing.
Resistance is a material’s tendency to resist the flow of charge (current).
When describing voltage, current, and resistance, a common analogy is a water tank. In this
analogy, charge is represented by the water amount, voltage is represented by the water pressure,
and current is represented by the water flow. So for this analogy, remember:



Water = Charge
Pressure = Voltage
Flow = Current
Consider a water tank at a certain height above the ground. At the bottom of
this tank there is a hose. The pressure at the end of the hose can represent
voltage. The water in the tank represents charge. The more water in the tank,
the higher the charge, the more pressure is measured at the end of the hose.
We can think of the amount of water flowing through the hose from the tank as
current. With water, we would measure the volume of the water flowing through the hose over a
certain period of time. With electricity, we measure the amount of charge flowing through the circuit
over a period of time. Current is measured in Amperes (usually just referred to as “Amps”). Amps are
represented in equations by the letter “I”.
Name: ___________________________
Date: _______________
Block: _______
What if we had two tanks but one has a narrow pipe and one has a
wide pipe.
It stands to reason that we can’t fit as much volume through a narrow
pipe than a wider one at the same pressure. This is resistance. The
narrow pipe “resists” the flow of water through it even though the
water is at the same pressure as the tank with the wider pipe.
In electrical terms, this is represented
by two circuits with equal voltages and different resistances. The circuit
with the higher resistance will allow less charge to flow, meaning the
circuit with higher resistance has less current flowing through it.
Ohm defines the unit of resistance of “1 Ohm” as the resistance
between two points in a conductor where the application of 1 volt will
push 1 amp. This value is usually represented in diagrams with the greek
letter “Ω”, which is called omega, and pronounced “ohm”.
Ohm’s Law relates the voltage, current and resistance of a circuit. It is represented with the
mathematical formula:
V = I∙R
In this virtual lab you will be investigating how changing the voltage and resistance affect the current
flowing through a circuit.
Background Questions:
1. Ohm’s Law shows the relationship between what factors of a circuit? ______________________
________________________________________________________________________
2. In the analogy using the water tank, what property of a circuit was represented by the volume
of water? ________________________________________________________________
3. What
is
Voltage:
___________________________________________________________
________________________________________________________________________
4. In the water analogy, how does narrowing a pipe affect how well the water can flow through it?
________________________________________________________________________
a. How does the analogy translate to electricity? _______________________________
__________________________________________________________________
5. What “Letter” represents resistance on a diagram? _________________________________
Name: ___________________________
Date: _______________
Block: _______
To start the lab-do one of the following
1.
Go to Mr. White’s Website at Sterling Middle School
 Select Online/Virtual Labs menu on the left side of the screen.
 Click Website Link under Unit 5: Electricity and Magnetism for Ohm’s Law Lab.
2. Go directly to the website below

https://phet.colorado.edu/sims/html/ohms-law/latest/ohms-law_en.html
Experiment 1: How Voltage Affects Current
Procedure:
1. Move the slider for Resistance on the ride side of the screen. Set the resistance for a value
between 490 Ohms and 510 Ohms. Record the value you are using the in the observation
table. This value should remain constant for each trial of the experiment.
2. Set the voltage to 1.5 V. This represents one AA battery hooked up to a circuit. Record the
value of the current flowing through the resistor. This value is being recorded in milliamps.
3. Increase the voltage to 3.0 V. Record the value of the current in the observation table.
4. Continue increasing the voltage 1.5 V until you have reached 9.0 V. Each time recording the
current flowing through the resistor. Complete the observation table.
Trials
Resistance (Ω)
Voltage (V)
1
1.5
2
3.0
3
4.5
4
6.0
5
7.5
6
9.0
Current (mA)
Current (A)
Analysis:
1. Convert the current from milliamps to amps. Record the new values in the observation
table above.
2. Identify the Independent Variable, Dependent Variable and a constant in this experiment.
a. I.V. : _________________________________
b. D.V.: ________________________________
c. Constant: ____________________________
Name: ___________________________
Date: _______________
Block: _______
3. Create a Scatter Plot Graph showing the relationship between Voltage and Current (in
Amps).
4. What type of relationship is between Voltage and Current? Direct or Inverse? ____________
5. Based on YOUR GRAPH, how much current would flow through the resistor if the voltage
was only 5.0 V? ________________________________________________________
6. Calculate the slope of your line of best fit.
7. Does the slope of the graph and the value of the resistor match? __________________
a. Should they?
Explain: _____________________________________________
_______________________________________________________________
_______________________________________________________________
Name: ___________________________
Date: _______________
Block: _______
Experiment 1: How Resistances Affects Current
Procedure:
1. Move the slider for Voltage on the ride side of the screen. Set the voltage for 5.0 V. Record
the value you are using the in the observation table. This value should remain constant for
each trial of the experiment.
2. Set the resistance to a value around 200 Ohms. Record the Actual resistance in the
observation table.
3. Record the value of the current flowing through the resistor. This value is being recorded in
milliamps.
4. Increase the resistance 5 times, you can choose whatever values you want, but they must
be greater than 200 Ohms. Each time you change the resistance; record the current flowing
through the resistor.
Trials
Resistance (Ω)
Voltage (V)
Current (mA)
Current (A)
1
2
3
4
5
6
Analysis:
1. Convert the current from milliamps to amps. Record the new values in the observation
table above.
2. Identify the Independent Variable, Dependent Variable and a constant in this experiment.
b. I.V. : _________________________________
c. D.V.: ________________________________
d. Constant: ____________________________
Name: ___________________________
Date: _______________
Block: _______
3. Create a Scatter Plot Graph showing the relationship between Resistance and Current (In
Amps).
1. What type of relationship is between Voltage and Current? Direct or Inverse? ____________
2. According TO THE GRAPH, does the relationship look linear? __________________________
3. Why can’t the graph go below zero on the Y-axis: _______________________________
______________________________________________________________________
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