Factors Affecting Electrical Resistance
INTRODUCTION:
Metals are generally excellent conductors of heat and electricity. Because of
this, we tend to neglect any resistance in wires when we examine the
behavior of ord
...
Factors Affecting Electrical Resistance
INTRODUCTION:
Metals are generally excellent conductors of heat and electricity. Because of
this, we tend to neglect any resistance in wires when we examine the
behavior of ordinary loads (bulbs, resistors, motors, etc.) in electrical circuits.
But metals are not perfect conductors, otherwise the wires in our toasters
would not get hot. In this experiment, you will examine the factors that affect
the electrical resistance of metals.
R = ρ (L/A)
OBJECTIVE:
The purpose of this experiment is to collect the potential difference and
current data for various metal rods and determine the electrical resistance
for each of the readings for the rods. Then determine how the length, crosssectional area, and type of material affect the resistance of the metal rods.
MATERIALS:
Vernier data-collection
interface
Vernier Resistivity Rod Set
Conventional power supply
Logger Pro or LabQuest App
Vernier Current Probe
Ruler in centimeters
Vernier Instrumentation
Amplifier
clip leads
a. Lab Set-UpPROCEDURE:
Setup using conventional power supply and Lab-Pro
1. Connect a Vernier Current Probe to the interface. Connect the current
probe in series to the negative terminal on the power supply and to
one end of the brass rod (see Figure 3).
2. Connect an Instrumentation Amplifier to the interface. Set the range to
0–20 mV. Use a lead to connect the black post on the instrumentation
amplifier to ground (usually the black terminal on the power supply).
Start the data-collection program.
3. Connect clip leads to the red and black terminals of the
instrumentation amplifier; these will act as the probe leads for your
measurements of potential. Connect the black lead to a position just
inside the lead carrying current to the rod. Note this as the zero
position. Touch the other lead (hereafter referred to as the red lead) to
the black lead on the rod and zero both sensors (see Figure 3).
4. Your instructor will provide specific instructions that will enable you to
run a DC current of approximately 0.5 A through the rod.
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