Bilash Physics
Ohm, Ohm on the Range Lab (Concepts) II
An Exploration of Resistors in Series
The simplest series circuit consists of a source of voltage and a resistor connected in a single loop. A series
circuit may also be made of multiple resistors connected in series, or end to end. In this activity you will,
• Determine the total resistance in a series circuit.
• Determine what happenes to the currents and voltages across the resistors in a series circuit.
Objective
Determine the relationship between the current, I and the voltage, V across each resistor in a series circuit.
Materials Provided
• Multimeter
• Resistor Board, (3-100kΩ, 1-200kΩ)
•
•
Three alligator clip wires
Battery
Procedure & Observations
DO NOT LEAVE ANY CIRCUIT CONNECTED FOR MORE THAN 10 SECONDS, OTHERWISE
THE BATTERIES WILL HEAT UP AND BURN OUT.
Part 1] Determining the Resistance of a One Resistor Series Circuit.
1.
Connect a 100kΩ resistor in series with a battery. Use a multimeter set at DCA200 µA to measure the current entering and exiting the resistor. (1µA = 10-6A).
I = __________ µA = ____________ A
2.
Use a multimeter set at DCV-20 to measure the voltage across the resistor.
V = __________ volts
3.
Calculate the resistance of the resistor in this circuit using Ohm’s law. (I = V/R)
(be sure to use the A reading – not the µA reading)
(note, k= “x1000”, so 100 kΩ = 100,000 Ω)
R = __________Ω
How does your calculation compare to the manufactures rated value?
4.
Series circuit
If you are not
familiar with
using a
multimeter, please
refer to the
handout
explaining how to
use a mulitmeter
to measure current
and voltage.
Draw two circuit diagrams for this circuit. One including the ammeter and one including the
voltmeter.
© 2015 Borislaw Bilash II. All rights reserved.
Part 2] Comparing I, R & V in a Three Resistor Series Circuit.
1.
Connect three resistors in series with a battery: two 100Ω and one 200Ω. Use a multimeter
set at DCA-200 µA to measure the current entering and exiting each resistor. (1µA = 106
A).
I1 = __________ µA = ____________ A
I2 = __________ µA = ____________ A
I3 = __________ µA = ____________ A
How does the current through the circuit in Part 1 compare to the current in a 3-resistor circuit?
2.
Use a multimeter set at DCV-20 to measure the voltage across each resistor.
V1 = __________ volts
V2 = __________ volts
V3 = __________ volts
How does the voltage through the circuit in Part 1 compare to the current in a 3-resistor circuit?
3.
With the battery connected with the circuit, measure the voltage of the battery.
VB = __________
What is the relationship between the voltage across the battery and the voltage drop across each resistor?
4.
Calculate the resistance of each resistor in this circuit using Ohm’s law.
R1 = __________Ω
R2 = __________ Ω
R3 = __________ Ω
What is the relationship between I1, I2 and I3 in this series circuit? (Are they the same or do they add up somehow?)
What is the relationship between R1, R2 and R3 in this series circuit? (Are they the same or do they add up
somehow?)
© 2015 Borislaw Bilash II. All rights reserved.
Follow-Up Questions:
(copy the questions down in your notebook)
1] What happens to the current in a one battery circuit if you add more and more
resistors?
2] In a series circuit with two or more resistors, how does the current in one resistor
compare with the current in the adjacent resistor?
3] In a series circuit with two or more resistors, how does the voltage through one
resistor compare with the voltage in the adjacent resistor?
4] State the formula to calculate the restance of a resistor if you measure the current and
voltage of the resistor.
5] If you repalced the resitors with light bulbs but still used only one battery, what
happens to the brightness of the bulbs if you add more lightbulbs in series?
6] A circuit is made of one light bulb and one battery. What could you add or remove
from the circuit in order to make the light bulb brighter?
© 2015 Borislaw Bilash II. All rights reserved.