physics
Physics 196 VirtuLab: Lorenz Force
Name:
Lab Day:
Overview
Explore the behavior of a charged object moving in a uniform magnetic field.
Mathematical Models and Assumptions
A moving charged particle experiences a Lorenz force given by F⃗B=q v⃗ x B⃗ . Since the force
produced is perpendicular to both velocity and magnetic field, uniform circular motion results.
An amu is an ‘atomic mass unit’ and has a value of 1.6610-27 kg.
Data Collection
Visit this URL: http:
www.thephysicsaviary.com/Physics/Programs/Labs/ChargeinMagFieldLa
Click ‘Begin’ to launch the simulation. You will need to modify
most of the settings before collecting data.
Click ‘Charge is -’ to change it to ‘Charge is +’.
Click ‘Magnitude of charge is 1e’ several times until it displays
‘Magnitude of charge is 5e’.
Click on ‘Grid is off’ to change it to ‘Grid is on’.
Click the a
ows beneath ‘Charge Speed’ to set it at 400 km/s.
Click the a
ows beneath ‘Charge’s Mass’ to set it at 18 amu.
Click the a
ows beneath ‘Field Strength’ to set it at 130 mT.
Part I. O
ital Radius and Magnetic Field Strength
Click ‘Fire’ to launch the particle into the region of uniform magnetic field. Measure the
diameter of the circular path it travels and record the result in Data Table One. Repeat the
process for different strengths of magnetic field from 130 mT to 400 mT, recording the diamete
of the path traveled each time.
Data Table One
Magnetic Field (mT) Diameter (cm) Charge (C)
130
Mass (kg)
Speed (m/s)
400
© Claude Mona, 2020. Last Edit: 25/01/21 12:30:48
http:
www.thephysicsaviary.com/Physics/Programs/Labs/ChargeinMagFieldLa
Physics 196 VirtuLab: Lorenz Force
Start with the expressions for the Lorentz force on a moving charged particle and the condition
for uniform circular motion. Derive an expression for the radius of the circular path in terms of
the magnetic field and other variables in the space below.
Based on your expression, does the radius have a linear relationship to the magnetic field?
Explain using complete sentences in the space below.
Using a Cartesian coordinate system, construct a graph of o
ital radius as a function of
magnetic field. Attach the graph to your completed report. Does the shape of the graph confirm
your explanation about the relationship between ‘R’ and ‘B’?
In order to ‘straighten out’ the data, you may note that the relationship you derived is of the
form R = CBn, where ‘R’ is the o
ital radius, ‘B’ is the magnetic field and ‘C’ is a proportionality
constant. As we know from 195, any expression with an exponential dependence may be
epresented as a straight line on a logarithmic scale. In the space below, start with the
expression for R and take the log10 of both sides. Continue manipulating the expression until you
have a linear expression for o
ital radius in terms of the magnetic field and the proportionality
constant. Show/explain each step.
Comparing the expression you have just created to the one derived at the top of this page, what
is the expected value of the slope?
© Claude Mona, 2020. Last Edit: 25/01/21 12:30:48
Physics 196 VirtuLab: Lorenz Force
Comparing the expression you have created to the one derived at the top of the previous page,
what quantities are included in your proportionality constant ‘C’? Calculate the expected value
of C (with units) in the space below.
Using a log10 scale for each of the axes, construct a graph of o
ital radius as a function of
magnetic field. Calculate the slope of your best-fit line on the graph. Determine the value of ‘C’
on the graph as well. Attach the graph to your completed report.
Compare the expected slope and C values to those obtained from your graph. Calculate the
percent (e
or or difference, as appropriate) for each of these comparisons.
© Claude Mona, 2020. Last Edit: 25/01/21 12:30:48