Ohm's Law Story
Problems
Ohm's Law states
that the voltage in a circuit is directly related
to the current flowing through the circuit and the
resistance provided by the circuit. Voltage is
defined as the potential energy difference from one
end of the circuit to the other. Voltage is similar
to water pressure. It measures how much energy is
pushing the electrons through the wire. Voltage is
measured in volts. Current is defined as the amount
of electricity flowing through a circuit. The more
electrons go through the wire, the higher the
current. Current is measured in amperes, sometimes
called amps. Resistance is a property of the
circuit itself. It is a measure of the difficulty
of the path that the electrons are following.
Resistance is measured in ohms. The equation
V=I•R describes the relationship between the
voltage on a circuit, the current flowing through
it and the resistance of the circuit. The V stands
for voltage, I for current (Inductant) and R for
resistance. The equation can be used to solve for
voltage in story problems when current and
resistance are given. The equation can be
re-arranged to solve for other variables. The
equation to use, when solving for current is I = V
/ R. resistance can be solved for using the
equation R = V / I.
To review, the
three forms of the velocity equation
are:
|
V
= I•R
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I
= V / R
|
R
= V / I
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When solving these
types of problems it is important to follow these
four steps:
- Select the
correct equation, and write it down.
- Re-write the
equation, inserting the values from the story
for the variables.
- Find the answer
and write it.
- Include the
correct units on the answer.
For example:
Problem #
1
A small electrical
pump is labeled with a rating of 3 amps and a
resistance of 40 ohms. What voltage was it meant to
run at?
|
Follow the
steps:
- Select
the correct equation, and write it
down.
- Re-write
the equation, inserting the values from
the story for the
variables.
- Find
the answer and write it.
- Include
the correct units on the
answer.
|
|
The
Solution:
- Select the
correct equation, and write it down. The correct
equation is V=I•R
- Re-write the
equation, inserting the values from the story
for the variables. The equation is re-written V
= 3 • 40.
- Find the answer
and write it. The answer is 120.
- Include the
correct units on the answer. The correct units
are volts.
Problem #2
A nine volt battery
is hooked up to a light bulb with a rating of three
ohms. How much current passes through the
light?
|
Follow the
steps:
- Select
the correct equation, and write it
down.
- Re-write
the equation, inserting the values from
the story for the
variables.
- Find
the answer and write it.
- Include
the correct units on the
answer.
|
|
The
Solution:
- Select the
correct equation, and write it down. The correct
equation is I = V / R.
- Re-write the
equation, inserting the values from the story
for the variables. The equation is re-written I
= 9 / 3.
- Find the answer
and write it. The answer is 3.
- Include the
correct units on the answer. The correct units
are amps.
Problem #3
A lamp is plugged
into the wall outlet, which is providing 110 volts.
An ammeter attached to the lamp shows 2 amps
flowing through the circuit. How many ohms of
resistance is the lamp providing?
|
Follow the
steps:
- Select
the correct equation, and write it
down.
- Re-write
the equation, inserting the values from
the story for the
variables.
- Find
the answer and write it.
- Include
the correct units on the
answer.
|
|
The
Solution:
- Select the
correct equation, and write it down. The correct
equation is R = V / I.
- Re-write the
equation, inserting the values from the story
for the variables. The equation is re-written R
= 110 / 2.
- Find the answer
and write it. The answer is 55.
- Include the
correct units on the answer. The correct units
are ohms.
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