Download Resistor Circuits Lab

Name: ________________________________
PHYC 101
Summer 2016
RESISTANCE AND RESISTOR CIRCUITS
Objectives:
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use a computer simulation to construct simple resistor circuits
examine how changes in resistance affect current
examine how changes in battery voltage affect current
use simulated multi-meters to measure current through,
and potential difference across, one or more resistors
determine the result of connecting resistors in series
determine the result of connecting resistors in parallel
Background:
Resistance is defined to be the ratio of electric potential difference (voltage) to current. When the electric
potential difference is measured in Volts and the current is measured in Amps, the resistance will be measured
in Ohms.
Materials:
Circuit Construction Kit found at http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
Example: 3 resistors in parallel
This free computer simulation allows you to construct resistor
circuits in multiple arrangements, choose the battery’s electric
potential difference, and choose each resistor’s resistance. You will
get better results if you choose these values carefully. The
simulation’s voltmeter and non-contact ammeter can be used to
obtain readings of these values for the entire circuit and for each
circuit element. Since the non-contact ammeter only records to the
hundredths place, you should make your battery voltage high
enough to give you current readings greater than 1.00 A, but not
so high that it “catches fire.”
The following suggestions will help you immensely in building your circuits, determining potential
difference and current, and responding to the lab questions.
 To determine the total current in a circuit, place the non-contact ammeter over the wire
immediately after the power supply.
 To determine the current entering a resistor, place the non-contact ammeter over the wire
immediately before the resistor.
 To determine the current leaving a resistor, place the non-contact ammeter over the wire
immediately after the resistor.
 To determine the total potential difference (voltage) in a circuit, place the voltmeter in parallel
across the power supply.
 The total resistance of a circuit will be the circuit’s total voltage divided by its total current (RT
= VT/IT).
 To determine the potential difference (voltage) across a particular resistor, place the voltmeter
in parallel across that resistor.
 “Right-clicking” on a circuit element gives you options for changing values, deleting, etc…
 Using the “Non-Contact Ammeter” will save you a lot of time!
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Name: ________________________________
PHYC 101
Summer 2016
Your answers to the questions in this lab activity are to be posted on Blackboard. Go to
Blackboard and select Resistor Circuits Laboratory Activity. You only get one opportunity to
receive a score on this lab activity, so choose your responses carefully and do not exit
Blackboard before recording all of your responses.
A Single Resistor
Use the computer simulation to construct a simple
circuit containing a battery (power supply), a switch,
wire, and a single resistor. Use a voltmeter and
an ammeter in the circuit so that the circuit’s total
voltage and total current can be determined, as well
as the current and voltage of the resistor. Manipulate
the battery’s voltage and the resistor’s resistance in
order to answer the following questions.
1. How do changes in the battery’s electric potential difference (voltage) affect the total voltage of the
circuit?
2. How do changes in the battery’s electric potential difference (voltage) affect the voltage across the
single resistor?
3. How does the current entering the power supply compare with the current leaving the power
supply?
4. How does the current entering the resistor compare with the current leaving the resistor?
5. What happens to the total current in the circuit as the resistor’s resistance is increased?
6. What happens to the voltage across the resistor as the resistor’s resistance is increased?
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Name: ________________________________
PHYC 101
Summer 2016
Multiple Resistors in Series
Use the computer simulation to construct a simple
circuit containing a battery (power supply), a switch,
wire, and multiple resistors in series. Use a voltmeter
and an ammeter in the circuit so that the circuit’s total
voltage and total current can be determined, as well
as the current through and voltage across the individual
resistors. Manipulate the battery’s voltage and the resistors’
resistances in order to answer the following questions.
7. Examine the total current when the circuit has a single resistor, two resistors in series, three
resistors in series, etc… What happens to the total current in the circuit as more and more
resistors are connected in series?
8. What is the relationship between the total resistance in a circuit and the resistance values of the
individual resistors when multiple resistors are connected in series?
9. What is the relationship between the total voltage in the circuit and the voltages across the
individual resistors?
10. What is the relationship between the total current in the circuit and the current through each
individual resistor?
Equal Resistors in Parallel
Use the computer simulation to construct a simple
circuit containing a battery (power supply), a switch,
wire, and multiple resistors in parallel. Use a voltmeter
and an ammeter in the circuit so that the circuit’s total
voltage and total current can be determined, as well
as the current through and voltage across the individual
resistors. Manipulate the battery’s voltage and the
resistors’ resistances in order to answer the following
questions. Each resistor should have the same
resistance value in this section.
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Name: ________________________________
PHYC 101
Summer 2016
11. Examine the total current when the circuit has a single resistor, two equal resistors in parallel,
three equal resistors in parallel, etc… What happens to the total current in the circuit as more and
more identical resistors are connected in parallel?
12. What is the relationship between the total resistance in a circuit and the resistance values of the
individual resistors when multiple resistors having identical resistances are connected in parallel?
13. What is the relationship between the total voltage in the circuit and the voltages across the
individual resistors?
14. What is the relationship between the total current in the circuit and the current through each
individual resistor?
Unequal Resistors in Parallel
Use the computer simulation to construct a simple
circuit containing a battery (power supply), a switch,
wire, and multiple resistors in parallel. Use a
voltmeter and an ammeter in the circuit so that the
circuit’s total voltage and total current can be
determined, as well as the current through and
voltage across the individual resistors. Manipulate
the battery’s voltage and the resistors’ resistances
in order to answer the following questions. Each
resistor should have different resistance value in
this section.
15. Examine the total current when the circuit has a single resistor, two unequal resistors in parallel,
three unequal resistors in parallel, etc… What happens to the total current in the circuit as more
and more unequal resistors are connected in parallel?
16. What can you say about the total resistance in a circuit when more than one resistor is connected
in parallel if the resistors are not identical?
17. What is the relationship between the total voltage in the circuit and the voltages across the
individual resistors?
18. What is the relationship between the total current in the circuit and the current through each
individual resistor?
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Name: ________________________________
PHYC 101
Summer 2016
Resistors in Combination
Many circuits contain resistors that are not totally
in series or totally in parallel. Use the simulation to
construct a circuit containing a battery comprised of
several dry cells in series, an ammeter, a switch, a
voltmeter, and two identical resistors in parallel
(R1 and R2) that are in series with an additional
resistor (R3). Manipulate the values of the 3
resistors (always keeping R1 = R2) in order to develop
a method for determining the total resistance of this
combination circuit.
Experiment with various values until you establish a method for determining the total resistance when
3 resistors are in this type of arrangement.
19. What is the total resistance when R1 = R2 = ? Ohms and R3 = ? Ohms?
20. What is the total resistance when R1 = R2 = ? Ohms and R3 = ? Ohms?
Summary Questions #21-24 will appear on Blackboard.
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