Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 123L
Section:
Analog Galvanometers
Part 1: Galvanometer Characteristics
Table 1: Galvanometer Characteristics
Voltage at full scale deflection, V (volts)
Resistance at half scale deflection, h (Ohms)
Current necessary for full scale deflection, Ig ( A)
Calculation: Current necessary for full scale deflection of galvanometer, Ig
TURN ALL POWER SUPPLY DIALS COUNTERCLOCKWISE (LEFT). TURN THE
POWER OFF AND DISCONNECT ALL LEADS.
Part 2: Voltmeter
Calculation: Multiplier resistance, M (for a voltmeter with a full scale deflection for 3.0 volts)
Eqn 1.
SET THE MULTIPLIER RESISTANCE TO YOUR CALCULATED VALUE BEFORE
CONNECTING THE POWER SUPPLY. CONSTRUCT THE VOLTMETER FOLLOWING
FIGURE 2 IN LAB MANUAL.
Table 2: Using the Galvanometer as a Voltmeter
Power Supply Voltage,
Galvanometer
Galvanometer
V (Volts)
Reading (divisions) Voltage, Vg (Volts)
3.0
±
±
2.5
±
±
2.0
±
±
1.5
±
±
1.0
±
±
0.5
±
±
0.1
±
±
Percent
difference (%)
*** Do NOT include uncertainty when calculating percent difference. ***
Lab: Analog Galvanometers
Updated 5/08/14
Data & Reporting score:
Sample calculation corresponding to power supply voltage of 2.0 volts: Translate your
galvanometer reading into voltage with uncertainty. Remember that your voltmeter is supposed
to have 3.0 V at maximum deflection (500 divisions). Don’t forget units and to round properly.
Galvanometer voltage =
NOW MEASURE THE VOLTAGE ON A BATTERY USING YOUR GALVANOMETER
VOLTMETER (POWER SUPPLY DIALS COUNTERCLOCKWISE. TURN THE POWER
OFF. DISCONNECT LEADS FROM POWER SUPPLY AND TOUCH ONE LEAD TO
EITHER SIDE OF THE BATTERY).
Table 3: Measuring the Voltage of a Battery Using a Galvanometer Voltmeter
Battery #
Multimeter voltage reading from instructor (volts)
Galvanometer Reading (divisions)
Calculated battery voltage (volts)
Percent difference (%)
TURN ALL POWER SUPPLY DIALS COUNTERCLOCKWISE (LEFT). TURN THE
POWER OFF AND DISCONNECT ALL LEADS.
Part 3: Ammeter
Calculation: Shunt resistance, s (for an ammeter with a full scale deflection for 3.0 A)
Eqn 2.
Calculation: Length of piece of #22 copper wire with resistance, s, calculated above. (#22
copper wire resistance = 0.00053 Ω/cm) Don’t forget units!
Length = s / (.00053 Ω/cm) =
(
)/(.00053 Ω/cm) =
HAVE THE INSTRUCTOR APPROVE YOUR CALCULATED LENGTH BEFORE
CUTTING THE COPPER WIRE.
__________ Instructor initials.
CONNECT YOUR WIRE TO THE GALVANOMETER FOLLOWING LAB MANUAL
DIRECTIONS BEFORE CONNECTING THE POWER SUPPLY. CONSTRUCT THE
AMMETER FOLLOWING FIGURE 3 IN LAB MANUAL.
Lab: Analog Galvanometers
Updated 5/08/14
Table 4: Using the Galvanometer as an Ammeter
Power Supply Current,
Galvanometer
Galvanometer
I (A)
Reading (divisions)
Current, Ig (A)
3.0
±
±
2.5
±
±
2.0
±
±
1.5
±
±
1.0
±
±
0.5
±
±
0.1
±
±
Percent
difference (%)
*** Do NOT include uncertainty when calculating percent difference. ***
Sample calculation: Translate your galvanometer readings into current with uncertainty, and put
the results into the right column in Table 4. Remember that your ammeter is supposed to have
3.0 A at maximum deflection (500 divisions). Don’t forget units and to round properly.
Galvanometer current =
Don’t forget to write your conclusion/summary! (Some things to think about … Start with an
introductory sentence stating the purpose/goal(s) of the lab. Did your readings of voltage and
current from your galvanometer come close to the standard readings from the power supply?
Consider percent difference. Are all of your voltage (and/or current) readings consistently high
or consistently low or inconsistent)? If the values are consistently high or low, what is the
probable source of error. Be specific. Also, how close did your galvanometer voltmeter come to
the multimeter reading for the voltage of a battery? Consider percent difference.)
Don’t
Write
Your
Conclusion
Paragraph
In
This
Space.
Use
An
Attached
Sheet
Of
Paper
Lab: Analog Galvanometers
Updated 5/08/14