Experiment 16-1 – Basic Direct Current (DC) Equipment

Name:
Physics II
Chapter 16
Experiment 16-1 – Basic Direct Current (DC) Equipment
Background/Theory:
We should be at the LAB TABLE with these devices somewhere close at hand to inspect them.
WATER ANALOGY
LOW VOLTAGE POWER SUPPLY
A battery is analogous to a pump in a water circuit. A pump takes in water at low pressure and does
work on it, ejecting it at high pressure. A battery takes in charge at low voltage, does work on it and
ejects it at high voltage.
Physics II – Experiment 16-1 – Basic Equipment – Page 2
The low voltage power
supply takes the place of
a battery.
The positive and negative
poles at the bottom right
of the image are the
anode and cathode.
VOLTMETER
A voltmeter measures the change in voltage between two points in an electric circuit and therefore
must be connected in parallel with the portion of the circuit on which the measurement is made
The voltmeters we
use have two scales:
1.5 Volts and 15
Volts depending on
the use and where
you connect the
alligator clips at
the base. This is
clearly marked.
Water Analogy
Straight edge screw used to
calibrate the meters. Rotate until
the device is zeroes if needed.
AMMETER
An ammeter is an instrument for measuring the electric current in amperes in a branch of an electric
circuit. It must be placed in series with the measured branch, and must have very low resistance to
avoid significant alteration of the current it is to measure. Uni-directional.
SCALE:
There are several
ammeter types
ranging in scale. You
may have to change
ammeters to match
the circuit.
Example:
Milliamps
Amps (1-15)
Physics II – Experiment 16-1 – Basic Equipment – Page 3
GALVANOMETER
Galvanometer is the historical name given to a moving coil electric current detector. When a current is
passed through a coil in a magnetic field, the coil experiences a torque proportional to the current.
The galvanometer has no units just representative numbers that indicated the strength and direction
of the current flow (it is bi-directional.)
RESISTORS
Resistors "resist" the flow of electrical current.
The higher the value of resistance (measured in
ohms) the lower the current will be.
Resistors are color coded. To read the color code
of a common 4 band 1K ohm resistor with a 5%
tolerance, start at the opposite side of the GOLD
tolerance band and read from left to right. Write
down the corresponding number from the color
chart below for the 1st color band (BROWN). To
the right of that number, write the
corresponding number for the 2nd band (BLACK) .
Now multiply that number (you should have 10) by
the corresponding multiplier number of the 3rd
band (RED)(100). Your answer will be 1000 or 1K.
It's that easy
Physics II – Experiment 16-1 – Basic Equipment – Page 4
CAPACITORS
A capacitor is an electrical/electronic device that can store energy in the electric field between a pair
of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging",
and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.
Common capacitor sizes as
compared to a 9-volt
battery.
The value of the
capacitors is printed on
the side usually in
microfarads.
These are UNIDIRECTIONAL.
(Identified by the longer
wire.)
Physics II – Experiment 16-1 – Basic Equipment – Page 5
DIGITAL MULTIMETER
A multimeter or a multitester is an electronic measuring instrument that combines several functions in
one unit. The most basic instruments include an ammeter, voltmeter, and ohmmeter.
We only have three multimeters, two that
work. Their operation is simple:
Plugs/Probes:
Depending on what you are measuring you
may need to plug the probes into a
different slot.
Switch:
Adjust the switch to whichever quantity
you are measuring.
SERIES AND PARALLEL CONNECTIONS:
The most basic type of wiring involves either series or parallel connections. The following text
and diagrams help illustrate these connections.
Two components are in Series with each other if only a single wire connects the end of one
component to the end of the other component. The wire connecting the two components cannot have
any other wire connected to it.
A component could be a capacitor, resistor, battery, or an inductor. More generally, a component
could also be a combination of components wired together in some fashion and considered to be a
single unit.
Physics II – Experiment 16-1 – Basic Equipment – Page 6
Two components are in Parallel with each other if their ends are connected together. The wires
connecting the ends of the components will each have a single wire connected to them running to some
other component.
In the above example, components one and three considered as a single unit are in parallel
with the second component. Also components one and three are in series with each other.
For example – Wiring Lamps and Batteries:
Lamps in series:
Each component has the same current. The battery voltage is divided
between the two lamps.
Each lamp will have half the battery voltage if the lamps are identical .
Lamps in parallel:
Each component has the same voltage. Both lamps have the
full battery voltage across them.
The battery current is divided between the two lamps.
Batteries in Series
To connect batteries in series link positive to negative terminals in a row. The voltage will sum and the
current will stay the same.
Batteries in Parallel
To connect batteries in parallel link all of the positive terminals and all of the negatives. The voltage
will stay the same but the current will sum.
Physics II – Experiment 16-1 – Basic Equipment – Page 7
SCHEMATIC DIAGRAMS:
Below are examples of schematic diagrams. Example schematics for parallel and series lamps
are shown on the previous page.
Procedure:
Using all of the information discussed above please complete each procedure
below. Please record data/observations as indicated as you work your way
through the procedure.
DO NOT AT ANY TIME TOUCH EXPOSED METAL
ALWAYS UNPLUG WHEN WORKING WITH THE POWER SUPPLY
Materials:
Low Voltage Power Supply
Voltmeter (±0.1V)
Ammeter (±0.1A)
Galvanometer
9-Volt Battery
C or D Cells in battery cradles
Alligator clip wires
Voltmeter and Ammeter readings should be to one place after the decimal!
Check the scale of the device you are using though.
Part 1 – Using the Low Voltage Power Supply and the Voltmeter
1. Have a low voltage power supply unplugged and turned off and set to 1.5 volts or the
lowest voltage setting. Make sure the meters are zeroed.
2. Using alligator clips, connect the positive on the power supply to the positive on the
voltmeter and the negative on the power supply to the 15 volt post on the voltmeter.
3. Plug the power supply in and turn on the power, notice the voltage on the voltmeter.
4. Slowly increase the voltage setting on the power supply and notice the setting on
the voltmeter. They are connected in parallel. It should indicate the same value.
5. Create a TABLE (Table #1) and record the values from the control and the readings
from the voltmeter – there should be ten or eleven settings/entries.
Physics II – Experiment 16-1 – Basic Equipment – Page 8
Part 2 – Using the Low Voltage Power Supply and the Ammeter.
1. Have a low voltage power supply unplugged and turned off and set to 1.5 volts or the
lowest voltage setting.
2. Use an ammeter with a scale of 0 to 15.
3. Using alligator clips, connect the positive on the power supply to the positive on the
ammeter and the negative on the power supply to the negative on the ammeter.
4. Plug the power supply in and turn on the power, notice the reading in amperes on the
ammeter.
5. Slowly increase the voltage setting on the power supply and notice the setting on
the ammeter.
6. Create a TABLE (Table #2) and record the voltage values from the control and the
readings from the ammeter – there should be ten or eleven settings/entries.
Part 3
1.
2.
3.
– Using the Galvanometer
Using two alligator clip wires connect the galvanometer to the LVPS (1.5V).
Record the value and the direction (R or L) of the deflection
Switch the wires to the opposite posts. Write your observation of what happens to
the needle on the gauge.
TEST YOUR BATTERIES
For the following portion of the lab – please test each battery to be sure that it has
1.4-1.6 volts. Use the digital multimeters (TURN THEM OFF WHEN YOU ARE DONE)
– place the ends of the probes on the cathode and anode of the battery, making sure
you are set to volts and the black wire is plugged into COM and the red into V. You
could also use a voltmeter.
Part 4
1.
2.
3.
4.
5.
6.
– Batteries in Series - Voltage
Create a TABLE (Table #3) to record this data.
Connect one D cell battery with the voltmeter (1-15 volt scale), record the value.
Connect two D cell batteries in SERIES with the voltmeter, record the value.
Connect three D cell batteries in SERIES with the voltmeter, record the value.
REPEAT FOR TWO MORE TRIALS.
Record a column for the average.
Part 5
1.
2.
3.
4.
5.
6.
– Batteries in Series - Ammeter
Create a TABLE (Table #4) to record this data.
Connect one D cell battery with the ammeter record the value.
Connect two D cell batteries in SERIES with the ammeter, record the value.
Connect three D cell batteries in SERIES with the ammeter, record the value.
REPEAT FOR TWO MORE TRIALS.
Record a column for the average
Physics II – Experiment 16-1 – Basic Equipment – Page 9
Part 6 – Batteries in Parallel – Voltmeter
1.
2.
3.
4.
5.
6.
Create a TABLE (Table #5) to record this data.
Connect one D cell battery with the voltmeter (1-15 volt scale), record the value.
Connect two D cell batteries in PARALLEL with the voltmeter, record the value.
Connect three D cell batteries in PARALLEL with the voltmeter, record the value.
REPEAT FOR TWO MORE TRIALS.
Record a column for the average.
Part 7 – Batteries in Parallel – Ammeter
1.
2.
3.
4.
5.
6.
Create a TABLE (Table #6) to record this data.
Connect one D cell battery with the ammeter record the value.
Connect two D cell batteries in PARALLEL with the ammeter, record the value.
Connect three D cell batteries in PARALLEL with the ammeter, record the value.
REPEAT FOR TWO MORE TRIALS.
Record a column for the average.
MAKE SURE ALL OF THE LIGHT BULBS IN THE LAMPS HAVE EQUALS RATINGS
(VOLTS AND AMPS AS PRINTED ON THE SIDE OF THE BULB!)
Part 8 – Lamps in Series – Voltage and Current
Section A – Constant Voltage – Record in Table 7A
1.
2.
3.
4.
5.
6.
7.
8.
9.
Connect a single lamp (light bulb in plastic or ceramic holder) to the low voltage power supply;
use the 1.5 V setting on the low voltage power supply.
Take note of its brightness (actually write down an observation.)
Use a multimeter to the appropriate settings. (20 V – DC Voltage and 200A – DC Amperage.)
(Ask if confused.) Touch the probes to the screws on the lamp and record the voltage, adjust
the multimeter and record the current. Do another trial for a total of two. Record in a
table (Table #7A)
Connect another lamp in series with the first – there should now be two in series.
Take note of the brightness of the two lamps in series (actually write down an observation.)
Using the multimeter probes, touch the clips to the screws on EACH lamp INDIVIDUALLY (2)
and record the voltage. Adjust then touch the multimeter probes to the screws on EACH lamp
INDIVIDUALLY (2) and record the current. Do another trial for a total of two. Record in
the table (Table #7) (You’ll have data for EACH lamp.)
Connect another lamp in series with the others – there should now be three in series.
Take note of the brightness of the three lamps in series (actually write down an observation.)
Using the multimeter probes, touch the clips to the screws on EACH lamp INDIVIDUALLY (2)
and record the voltage. Adjust then touch the multimeter probes to the screws on EACH lamp
INDIVIDUALLY (2) and record the current. Do another trial for a total of two. Record in
the table (Table #7) (You’ll have data for EACH lamp.)
Section B – Increasing Voltage - Record in Table 7B
1.
2.
3.
4.
5.
Starting with the 1.5 V setting on the LVPS, connect one bulb. Measuring with your
multimeter – how much voltage does the bulb get? Do one more trial.
Connect two bulbs in series to the LVPS – each gets how much voltage? Do one more trial.
Up the voltage to 3.0 V – how much voltage does each bulb receive now? Do two more trials.
Add one more bulb in series (there will be three bulbs now at 3.0 V) – how much voltage does
each bulb receive? Do one more trial.
Up the voltage to 4.5 V – how much voltage does each bulb receive now? Do one more trial.
Physics II – Experiment 16-1 – Basic Equipment – Page 10
Part 9 – Lamps in Parallel – Voltage and Current
1. Connect a single lamp (light bulb in plastic or ceramic holder) to the low voltage
power supply, use the 1.5 V setting on the low voltage power supply.
2. Take note of its brightness (actually write down an observation.)
3. Use a multimeter to the appropriate settings. (20 V – DC Voltage and 200A – DC
Amperage.) (Ask if confused.) Touch the probes to the screws on the lamp and
record the voltage, adjust the multimeter and record the current. Do another trial
for a total of two. Record in a table (Table #8)
4. Connect another lamp in parallel with the first – there should now be two in parallel.
5. Take note of the brightness of the two lamps in parallel (actually write down an
observation.)
6. Using the multimeter probes, touch the clips to the screws on EACH lamp
INDIVIDUALLY (2) and record the voltage. Adjust then touch the multimeter
probes to the screws on EACH lamp INDIVIDUALLY (2) and record the current. Do
another trial for a total of two. Record in the table (Table #8) (You’ll have data
for EACH lamp.)
7. (Table #8) (You’ll have data for EACH lamp.)
8. Connect another lamp in parallel with the others – there should now be three in
parallel.
9. Take note of the brightness of the three lamps in parallel (actually write down an
observation.)
10. Using the 1-15V voltmeter, touch the clips to the screws on EACH lamp
INDIVIDUALLY (3) and record the voltage. Adjust then touch the ammeter clips to
the screws on EACH lamp INDIVIDUALLY (3) and record the current. Do another
trial for a total of two. Record in the table (Table #8)
This is the end of the procedure.
Data:
You will have several tables and paragraph length observations as indicated for each part in the
procedure. Short synopses of these are as follows:
Part
Part
Part
Part
Part
Part
Part
Part
Part
1 – Table #1
2 –Table #2
3 – Observations
4 – Table #3
5 – Table #4
6 – Table #5
7 – Table #6
8 – Table #7A & #7B & Observations
9 – Table #8 & Observations
(An example of an appropriate
format for Table 7A and 8 using
three bulbs A, B, and C, are shown
to the right.)
Source
1.5V
Cell
Bulbs
A
Trial
1
A
A
B
2
1
A
B
2
A
B
C
1
A
B
C
2
Voltage (V)
Current (A)
Physics II – Experiment 16-1 – Basic Equipment – Page 11
Lab Report Guidelines – 50 Points
You should use the handouts given to you in the first week of school detailing how to write lab
reports. The following should also assist you. These will be followed the rest of the year. The labs may
be typed or handwritten (please only in black or blue ink or pencil! – This may cost you points.)
Heading/Title
Write your name, class, period, and date of experiment in the upper right corner.
Centered at the top middle of the page write the Title and Experiment Number.
Procedure
Materials List
Use a bulleted vertical list (do not list in sentence form) and include precision of all instruments that
have this characteristic.
Procedure
There will be NO written procedure.
Data (28 Points)
Each table is worth an indicated number of points. INCLUDE DESCRIPTIVE TITLES!
Part 1 – Table #1 - 2 points
Part 2 –Table #2 – 2 points
Part 3 – Observations – 2 points
Part 4 – Table #3 – 2 points
Part 5 – Table #4 – 2 points
Part 6 – Table #5 – 2 points
Part 7 – Table #6 – 2 points
Part 8 – Table #7A & #7B & Observations – 7 points (3 pts – observation – 4 pts – table)
Part 9 – Table #8 & Observations - 7 points (3 pts – observation – 4 pts – table)
Analysis/Conclusions (22 Points)
The questions listed below are guide questions. You ARE NOT to just number and answer the
questions but include the answers to the questions in your analysis; written as an essay in paragraph
form. If you just answer the following questions, you will only get half of the points.
Remember you are to write the conclusion for somebody who has NO background knowledge
of the experiment and to present your results.
INCLUDE DATA IN YOUR ANSWERS – NOT JUST ‘REFER TO TABLE…’
1. Basic/introduction – what type of circuits (DC or AC?), measuring tools, etc did you learn
about?
2. Voltmeter/Ammeter (Parts 1 and 2) – What did you observe when you tested each measuring
device? (Answer for each.)
3. Galvanometer (Part 3) – Describe the basic operation of this device – is it unidirectional?
Explain what happened in your trials? Any other observations?
4. Batteries in series - voltage (Part 4) – What did you observe? What can you conclude from
your observations?
5. Batteries in series – current (Part 5) – What did you observe? What can you conclude from
your observations?
6. Batteries in parallel - voltage (Part 6) - What did you observe? What can you conclude from
your observations?
7. Batteries in parallel – current (part 7A & 7B) - What did you observe? What can you conclude
from your observations?
Physics II – Experiment 16-1 – Basic Equipment – Page 12
8.
Bulbs in series – voltage and current (part 8) - What did you observe (brightness of the bulbs
& trends in data?) What can you conclude from your observations about both current and
voltage?
9. Bulbs in parallel – voltage and current (part 9) - What did you observe (brightness of the
bulbs & trends in data?) What can you conclude from your observations about both current
and voltage?
10. Error Analysis - Not only the errors but suggestions for improvement next time the lab is
conducted!
11. Conclusion/Synopsis – what did you learn?
Miscellaneous:
(-1 or more points)
(-1 or more points)
(-1 or more points)
(-1 or more points)
(-1 or more points)
– Writing in proper format. (Using paragraphs, verb agreement, etc.)
– Spelling (one or two misspellings are forgivable)
– Neatness and Readability (This includes if you do not use black or blue ink or pencil.)
- NO cover pages
- One side of the paper – please.