Download ohm`s Lab

Name: ________________ Partner: _____________________ Date: _____________________
SNC 1D
Verifying Ohm’s Law
Introduction
For a circuit to be complete it must include connecting wires, a power source, and a load. The
power source provides coulombs with energy which is measured in ________. The coulombs decrease
in energy as they pass through the load, providing the load with energy to create light, heat or perform
some sort of action. The connecting wires create a path allowing the coulombs to flow through the
circuit. The amount of coulombs moving through a point in the circuit in a certain amount of time is
referred to as the __________. ___________ is measured by an ammeter which is connected inside the
circuit. __________ (potential difference) is the amount of energy per coulomb of charge between 2
different points in the circuit. It is measured by a voltmeter which is connected across two points in a
circuit outside of the circuit (connected in parallel).
Ohm’s law states that the ratio between the voltage and current is constant for a given resistor.
Mathematically this is written as ____________.
In all experiments, variables are measured and controlled according to a strict set of rules. Only
2 variables can be analysed at a given time and so, all variables can be divided into
 Independent variable – the variable that is changed by the experimenter and sets up the
variable that is measured.
 Dependent variable – the variable that is measured during the experiment.
 Controlled variables – other factors that need to be monitored (controlled or kept as
constant as possible) for the purpose of consistency and so that the experimenter can
focus only on the relationship of the dependent and independent variable.
In this lab, the independent variable is voltage, the dependent variable is ________________.
List and describe some of the variables that must be controlled throughout the experiment.
Purpose:
To verify Ohm’s law for a resistor and to see if Ohm’s law applies to a light bulb
Materials:
Ammeter
Wires
Voltmeter
25  resistor
Power source
150  resistor
1
Switch
Light bulb
Method:
*SAFETY CONCERNS*:
1. Make sure the switch is open before you connect the meters
2. Never raise the voltage above 10V
Use the following method to build each of the circuits required in this lab.
A) Connect your circuit with 1 load, 1 ammeter, 1 voltmeter, and the switch open. Check with your teacher
before turning on the power supply. Note: the flow of charges has to be consistent with the meters
measuring. Check the path by imagining an electron moving through the circuit from the negative terminal
to the positive terminal of the power supply.
B) Turn the power source on to its lowest voltage and close the switch.
C) Measure the current with the ammeter and the voltage with the voltmeter. Record each measure in Table 1
(Observations on page 3) and Table 2 (Data Manipulation on page 3).
D) Increase the voltage slightly and repeat step C) until you have 5 measures recorded.
E) Replace the load and repeat steps A) – D) until you have experimented with all three loads.
Observations
Table 1:
Load 1 Voltage
Current
(V)
(A)
Load 2 Voltage
(V)
Load 3Voltage
(V)
Current
(A)
Current
(A)
Qualitative Observations
How did the loads feel when you disconnected them?
Describe the brightness of the light throughout the experiment?
Data Manipulation
Complete the following table based on your data from table 1.
Table 2:
Load 1 V
I
(V)
(A)
V/I
(Ω)
Load 2 V
I
(V)
(A)
V/I
(Ω)
2
Load 3V
(V)
I
(A)
V/I
(Ω)
Result Summary (no explanation required)
1. What happen to each the current value for each load as the current increased?
2. Was the V/I value “constant” for each load?
Discussion
Answer these questions in several paragraphs (at least one per question). Be as specific as possible
in your explanations!!
1. Explain your qualitative observation regarding the temperature of the loads and the brightness
of the bulb
2. Using your quantitative values in Table 2, make a conclusion about the validity of Ohm’s Law
– did your results suggest it is true for all loads.
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(Continue on lined paper if needed)
SNC 1D- Lab Marking Scheme
Sections
Level 1
Minimal
requirements
are met
Level 2
Some of the
requirements
are met
Inquiry
Level 3
Most of the
requirements
are met
Level 4
All of the
requirements
are met
Weight
Qualitative observations made
are clear and detailed
2x
Discussion
Qualitative observations from
PART A are explained fully
Discussion
Qualitative observations from
PART B are explained fully
Discussion
Conclusions about the effect of
changing resistance on current
are well explained
Discussion
Conclusions about effect of
changing voltage on current are
well explained
2x
2x
3x
3x
Overall Inquiry
/48
Communication
2x
Data Table 1 and 2
All values are included and are
clearly written
Diagrams
Include all components
involved in the circuit and show
movement of electrons
Spelling and grammar (used
full sentences)
2x
1x
/20
Overall Inquiry
4