Laboratory Report 2
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Transcript of Laboratory Report 2
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Group # : 3 DOP : _______
Preliminary Data Sheet
EE 281L
Experiment no. 2
Ohm’s Law Relationships
I. Objectives
1. For the student to verify ohm’s law by calculating, and then by measuring
voltage, current and resistance, and then comparing the calculated and
measured results.
2. For the student to verify ohm’s law relationships by increasing one quantity
while holding the second quantity constant, the measuring and calculating the
effect on the third quatity.
II. Equipment and Parts
Digital Multimeter (DMM),
Power supply
Resistor
Alligator clips
III. Information
The three forms of Ohm’s Law are:
The procedures in this experiment will have the student verify these formulas by
comparing measured data. Allow for a reasonable tolerance in your data. For
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example: Measured voltage = 15 V; Calculated voltage = 14.8 V. To compare these,
we use
Due to the accuracy of the measurement instruments (digital voltmeter,
digital ohmmeter about analog ammeter about ), measurements in the DC
laboratory that agree within may be considered equal for most purposes.
IV. Procedures
1. Perform the following steps to verify that
CURRENT = VOLTAGE DIVIDED BY RESISTANCE.
A. Measure the resistance of the 6.8 k Ω (color-coded value) resistor with the
DMM.
: 29.98 k Ω
B. Connect the circuit in Figure 1.
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C. Adjust the power supply voltage to 15.0 V using the DMM set on its DC
voltage mode.
D. Measure and record the voltage across the resistor.
E. Look carefully at Figure 2: the multimeter is incorrectly measuring VR1,
since it will read both the voltage across R1 AND the voltage across the
ammeter. Figure 3 shows the correct way to measure VR1. Make sure that
the voltage across R1 is still 15.o V (it MAY have dropped slight due to the
milliammeter).
F. Measure and record the current through R1. = 0.3µA
G. Using the measured values of voltage and resistance, calculate the current
through using OHM’s Law.
= 0.5 µA
H. What conclusion can you make from these procedures?
Current varies directly to the voltage and varies inversely to the
resistance.
2. Perform the following steps to verify that
RESISTANCE EQUALS VOLTAGE DIVEDED BY CURRENT:
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A. Connect the same circuit as in figure 3, except change the value of
resistance of 1.8 k Ω (color-coded value).
B. Measure and record the voltage across R1 and the current flow through
R1.
C. Calculate the resistance of R1 using the measured values of and
with Ohm’s Law.
D. Remove R1 from the circuit. Measure and record the resistance of R1
using the multimeter.
E. What conclusion can you make from these procedures?
Resistance varies directly to the voltage and varies inversely to the
current.
3. Perform the procedure to verify that
VOLTAGE EQUALS CURRENT TIMES RESISTANCE.
A. Connect the circuit in Figure 3, except change the resistor to 9.1 k Ω. (color-
coded value)
B. Measure the resistance of this resistor making sure that the resistor is
removed from the circuit.
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C. Reinsert the resistor into the circuit and measure the current through the
resistor.
D. Calculate, using Ohm’s Law, the resistor voltage using the measured values of
resistance and current.
E. Measure the resistor voltage.
F. What conclusion can you make from these procedures?
VOLTAGE VARIES RESISTANCE TO THE PRODUCT OF THE RESISTANCE AND
CURRENT
4. Perform the following procedures to verify that
IF THE RESISTANCE IS HELD CONSTANT, INCRESING THE VOLTAGE WILL
INCREASE THE CURRENT.
A. Connect the circuit in Figure 3 using a 1.8 k Ω resistor. Set the voltage
source to 10.0V.
B. Measure the current trough the resistor
C. Increase the voltage source to 20V and again measure the current through
the resistor
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D. Based on the results of this procedure, what conclusion can be made
about the relationship between voltage and current for a fixed value of
resistance?
As voltage increases, the current also increases.
5. Perform the following procedures to verify that
IF THE VOLTAGE IS HELD CONSTANT, INCREASING THE RESISTANCE WILL
DECREASE THE CURRENT.
A. CONNEC5T THE CIRCUIT IN Figure 3, using a 1.8 k Ω color coded resistor.
Set the voltage source to 10.0V.
B. Measure the current through the resistor.
C. Change the resistor value to 29.98 k Ω and again measure the current
through the resistor.
D. Based on the result of this procedure, what conclusion can be made about
the relationship between resistance and current for a fixed value of
voltage?
RESISTANCE VARIES INVERSELY TO THE CURRENT AS RESISTANCE
INCREASES.
6. Perform the following procedures to verify that
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IF CURRENT IS HELD CONSTANT, INCREASING THE RESISTANCE WILL
INCREASE THE VOLTAGE.
A. Connect the circuit in Figure 3, using R=1.8 k Ω. Adjust the source voltage so
that the current through the resistor measures 2.0mA.
B. Measure the source voltage.
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C. Change the resistor value to 29.98 k Ω. Again adjust the source voltage until the
current through the resistor measures 2.0mA.
D. Measure the source voltage.
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E. Based on the results of this procedure, what conclusion can be made about
the relationship between resistance and voltage for a fixed value of current?
THE RESISTANCE VARIES DIRECTLY TO THE VOLTAGE AS RESITANCE
INCREASES.
V. Data and Result
The actions in this experiment will verify the formula of ohm’s law by
evaluating measured data with calculated data. You can see our explanation in
the question above of what conclusion can you make from the procedures.
From the first verification that “current is equal voltage divided by
resistance”. In other words, the current is directly proportional to the voltage and
inversely proportional to the resistance. So, an increase in the voltage will
increase the current as long as the resistance is held constant. Alternately, if the
resistance in a circuit is increased and the voltage does not change, the current
will decrease.
From the second verification that “resistance equals voltage divided by
current”. It tells us that we can calculate the resistance in a circuit if the voltage
and current are known. If the current is held constant, an increase in voltage will
result in an increase in resistance. Alternately, an increase in current while
holding the voltage constant will result in a decrease in resistance.
From the third verification that “voltage equals current times resistance. It
tells us that the voltage can be calculated if the current and the resistance in a
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circuit are known. It can be seen from the equation that if either the current or
the resistance is increased in the circuit (while the other is unchanged), the
voltage will also have to increase.
VI. Observation
All the statement in this experiment was proven by carrying out a trial to the
three figures shown above. We used the Ohm’s law, and it defines the
relationships between power (P), voltage (E), current (I), and resistance. One ohm
is the resistance value through which one volt will maintain a current of one
ampere. I will include the relationships of them to each other in the conclusion
below.
VII. Conclusion
This experiment identifies the ohm’s law relationships. Meaning to say , how
voltage current , resistance relate.
First. It was based on my inspection that the use of alligator wires is for the
current (I), it flows on a wire or conductor like water flowing down a river. Current
flows from negative to positive on the surface of a conductor and measured in (A)
amperes.
Second. Voltage is the push or pressure behind current flow through a circuit,
and is measured in (V) volts. It is also the difference in electrical potential
between two points in a circuit.
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Third. A very high resistance allows a small amount of current to flow. A very
low resistance allows a large current to flow. It determines how much current will flow
through a component and.
Last. Power is the amount of current times the voltage level at a given point
measured in wattage or watts.
All of these variations of Ohm’s Law are mathematically equal to one another.
Kitt Rho Manarin Reynaldo Dela Cruz
Leader
Instructor