Electric Circuits Simulation Lab
I need to complete an online physics simulation lab worksheet. The worksheet has all the steps to follow. part the worksheet requires 4 simple excel graphs.
Titleof the Experiment: Electric Circuits
Student Name: ……………………………………………………………………… Date: ………………………………………….
Objectives:
1) To study the relationship between the electric current passing through a resistance and the
potential difference across it.
2) Use Ohms’ law to find the equivalent resistance of the different combinations of resistors.
3
) To distinguish between the Ohmic resistor and the non‐Ohmic resistor.
Apparatus: DC ‐ Power supply, voltmeter, ammeter, resistors, and connecting wires.
Theory and Background:
The electric field inside a conductor equals zero when it is at electrostatic equilibrium, but when the charges move in a conductor, they produce an electric current, which is defined by the current density (J). For an Ohmic material the ratio of the current density (J
=
I/A) and the electric field (E) is constant and equals the conductivity (σ ). Hence Ohms’ law can be written as:
J = σ E …………..………….. (1)
Where J is the current density, given by: J = I / A
I is the current, A is the cross sectional area of the conductor, E is the electric field and σ is the conductivity of the material, which is equal to inverse of the resistivity of the material (ρ),
σ = (1/ρ)
For a straight wire of cross sectional area (A = π R2; R is the radius of the wire) and length (L) and a potential difference (
V
) is maintained across it, E is given by the expression:
E = V/ L
Hence:
So that:
But ,
Hence: ……………….. (2)
Resistors are one of the main components of any electric circuit, and some circuits need more than one resistor to produce a high (or low) equivalent resistance. Depending on the purpose for which the circuit is built, resistors can be connected in
series
or in
parallel
. For two resistors, R1 and R2, the series and parallel connections, and the equivalent resistance, are shown in Figures 1 (a) and 1 (b).
For resistors connected in series:
Figure 1(a)
When the resistors are connected in parallel:
Figure 1(b)
Circuit Connection:
The circuit that we will use is shown in Figure 2
Figure 2: Circuit Diagram
To do the experiment by using PHET interactive simulation follow the following steps:
1) Click on the following link from PHET Colorado Simulation
https://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
2) Download Circuit Construction Kit: DC
3) Click on Lab
4) Choose Conventional Current
5) Use the components in the left side to build the circuit shown below:
Re (rheostat) Variable resistor
R1 = 5Ω
6) Click on the resistor (R1) and fix it at 5Ω. That is R1 = 5Ω.
7) Click on the Battery and fix it at 120V.
8) Click on the Voltmeter from the right side and drag it to measure (V1) the voltage across R1.
9) Click on the Ammeter from the right side and drag it and put it in series with R1 (before or after R1) to measure (I1).
10) Vary the rheostat () to obtain 6 different readings of the electric current (I) and the corresponding values of the voltage (V). Then Record the values into table 1.
11) Replace R1 by R2=10Ω as shown below:
12) Again vary the rheostat () to obtain 6 different readings of the electric current (I) and the corresponding values of the voltage (V). Then Record the values into table 1.
13) Connect R1=5Ω and R2=10Ω in series as shown below, and again vary the rheostat () to obtain 6 different readings of the electric current (I) and the corresponding values of the voltage (V). Then Record the values into table 1.
R1 and R2 in Series Connection
14) Now connect R1=5Ω and R2=10Ω in parallel as shown below, and also vary the rheostat () to obtain 6 different readings of the electric current (I) and the corresponding values of the voltage (V). Then Record the values into table 1.
R1 and R2in parallel connection
Note that the Voltmeter is always connected in parallel with the element while the Ammeter in series
Table (1)
|
R1 () |
R2 () |
Equivalent Resistance in series |
Equivalent Resistance
in parallel |
||||
|
V(V) |
I (A) |
||||||
1- Plot a graph V versus I for each case?
2- Does the best straight lines passes through the origin? Explain.
3- Calculate the slope of each graph and determine the resistance (R) from the graph (slope) and experimentally? Record the results into table 2.
Table (2)
|
Slope |
The experimental Resistance ( Ω ) |
δ % |
|
Graph 1 |
R1 experimentally = |
|
|
Graph 2 |
R2 experimentally = |
|
|
Graph 3 |
Req experimentally = |
|
|
Graph 4 |
4- What is the difference between Ohmic resistor and a Non-Ohmic resistor?
Ohmic:
Non-ohmic
5- When the potential difference, V, across an ohmic resistor is increased what effect does this have on:
a. The electric current (I)
b. The resistance (R)
Conclusions:
3
RI
V
=