Current Electricity Lab –Series/Parallel Circuits
Name ____________
Safety and Equipment Precautions!
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Plug in your power supply and use ONLY the D.C. terminals of the power source, NOT the A. C. terminals.
DO NOT touch wires together when the power supply is on.
DO NOT leave the circuit with the power supply on for long periods of time! The resistors get VERY hot
and may fry!
You must disconnect ALL wires from the resistor BEFORE you measure the Resistances of the resistors!
R=V/I
or
Procedure
Part 1 – “Creating Circuits”
1A. Using the SMALL wires, BULBS, and BATTERY, you and your electrician partner will build the following...
1. A circuit with two bulbs wired in Series.
2. A circuit with two bulbs wired in Parallel.
* HAVE YOUR CIRCUIT CHECKED BY Mr. Putnam FOR REGENTS CREDIT! *
Draw the circuits below that you have built making certain to use proper circuit symbols and labels!
(Use your Reference Table for assistance with the symbols.)
Series with 2 bulbs
Parallel with 2 bulbs
Part 2 – “Using Ohm’s Law in Series and Parallel Circuits”
IMPORTANT!
•
•
•
•
•
•
•
Plug in your power supply and use ONLY the D.C. terminals of the power source, NOT the A. C. terminals.
DO NOT touch wires together when the power supply is on.
DO NOT leave the circuit with the power supply on for long periods of time! The resistors get VERY hot
and may fry!
You must disconnect ALL wires from the resistor BEFORE you measure the Resistances of the resistors!
The Total Voltage ["Power Supply"] for both circuits must be set between 3 & 5 Volts.
[Be certain to enter the ACTUAL voltage in the table.]
You must disconnect the circuit BEFORE you measure the Resistances of the resistors!
Have your Physics teacher check your circuit before you measure your values.
SERIES CIRCUIT
Create a SERIES circuit using Resistor #1 & Resistor #3. Check the power supply FIRST with your
multimeter to be certain it is set between 3 & 5 Volts. Fill out the table below.
Voltage Table-Series Circuit
Measure the Voltage
across…
Resistor #1
Resistor #3
Total Voltage (R1 + R3)
Voltage [V]
TO TEST VOLTAGE…
Measure ACROSS THE
RESISTOR & set the
Multi-meter to the 20V
DC setting.
Current Table-Series Circuit
Measure the Current…
BEFORE Resistor #1
AFTER Resistor #3
Total Current in circuit
Current [I]
TO TEST CURRENT…
Set Multi-meter to the
10A setting with probe
wires plugged in as in
the above diagram.
Using YOUR values for Total Voltage & Total Current in the above tables,
CALCULATE the TOTAL RESISTANCE of the circuit using Ohm's Law.
Calculated Total Resistance of your Series Circuit à __________________
WITH THE WIRES REMOVED FROM THE RESISTOR(S)… MEASURE RESISTANCE
Measure with the Digital
Multimeter...
The Resistance of…
Resistor #1
Resistor #3
CALCULATED
Total Resistance of Circuit
[Using Ohm’s Law]
MEASURED
Total Resistance of Circuit
[Using the Multi-meter]
PERCENT ERROR between
the two Total Resistance
values.
Resistance [Ohms]
TO TEST RESISTANCE…
Set Multi-meter to the 200 Ω setting,.
WITH THE WIRES REMOVED FROM
THE RESISTORS BEFORE TESTING!
PARALLEL CIRCUIT
Create a PARALLEL circuit using Resistor #1 & Resistor #3. . Check the power supply to be certain
it is set between 3 & 5 Volts. Fill out the table below.
Voltage Table-Parallel Circuit
Measure the Voltage
across…
Resistor #1
Resistor #3
Total Voltage [Power supply]
Voltage [V]
Current Table-Parallel Circuit
Measure the Current…
BEFORE Resistor #1
AFTER Resistor #3
Total Current
TO TEST VOLTAGE…
Measure ACROSS THE RESISTOR &
set the Multi-meter to the 20V DC
setting.
Current [I]
TO TEST CURRENT…
Set Multi-meter to the 10A setting
with probe wires plugged in as in the
above diagram.
Using YOUR values for Total Voltage & Total Current in the above tables,
CALCULATE the TOTAL RESISTANCE of the circuit using Ohm's Law.
Calculated Total Resistance of your Parallel Circuit à __________________
WITH THE WIRES REMOVED FROM THE RESISTOR(S)… MEASURE RESISTANCE
Measure with the Digital
Multimeter...
The Resistance of…
Resistor #1
Resistor #3
CALCULATED
Total Resistance of Circuit
[Using Ohm’s Law]
MEASURED
Total Resistance of Circuit
[Using the Multi-meter]
PERCENT ERROR between
the two CALCULATED
Total Resistance values.
Resistance [Ohms]
TO TEST RESISTANCE…
Set Multi-meter to the 200 Ω setting
WITH THE WIRES REMOVED FROM
THE RESISTORS BEFORE TESTING!
Conclusions
Using your knowledge of electric circuits, answer the following…
#1-3à For SERIES circuits…
1.
A. What would happen to the Total Current of your circuit if you were to change from a two-bulb series
circuit to a three-bulb series circuit?
B. How could you tell from JUST LOOKING at the bulbs?
2. What would happen to the bulbs if one bulb blows out while doing the experiment?
3. What happens to the Total Resistance of your circuit if you added a bulb to the series circuit?
#4-6à For PARALLEL circuits…
4. A. What would happen to the Total Current of your circuit if you change from a two-bulb parallel circuit
to a three-bulb parallel circuit?
B. How could you tell from JUST LOOKING at the bulbs?
5. What would happen to the bulbs if one bulb blows out while doing the experiment?
6. What happens to the Total Resistance of your circuit when you change from a two-bulb parallel circuit
to a three-bulb parallel circuit?
7A. Why shouldn’t you wire your entire home ONLY in parallel?
7B. What would happen to the Total Current throughout the home?
7C. What would happen to the fuses or circuit breakers in your home?
8. For the Series Circuit, if R1 = 10Ω, R2 = 15Ω,
Ammeter A = 2A & the Total Voltage is 60V, find…
_______ = R3
_______ = Total Current
_______ = Total Resistance
_______ = Total Power
A
9. For the Parallel Circuit, if R1 = 10Ω, R2 = 25Ω, the
Voltage drop across R1 = 50V & the Ammeter A = 8A, find…
_______ = R3
_______ = Total Potential
Difference
_______ = Total Resistance
_______ = Total Power
A