Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Multiple-Choice Questions
Electricity Generation
Generating Electricity
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 1If the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing into the page)
va
dc
b
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 1 AnswerIf the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing into the page)
va
dc
b
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 1 ExplanationElectricity
Generation
Uniform B field (pointing into the page)
va
dc
b
Here, we see that the velocity is perpendicular to the magnetic field. We know therefore, that there will be a force that pushes the –ve charges in a direction perpendicular to BOTH the velocity AND the magnetic field – either toward a or toward b. To determine which of the two directions, use the right hand rule point your fingers in the direction of the field (into the page), face your palm in the direction of the velocity (to the left) and your thumb will point in the direction of motion of the –ve charges : toward a.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 2If the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing into the page)
va
d
cb
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 2 AnswerIf the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing into the page)
va
d
cb
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 2 ExplanationElectricity
Generation
Uniform B field (pointing into the page)
va
d
cb
Here, we see that the velocity is perpendicular to the magnetic field. We know therefore, that there will be a force that pushes the –ve charges in a direction perpendicular to BOTH the velocity AND the magnetic field – either toward a or toward b. To determine which of the two directions, use the right hand rule point your fingers in the direction of the field (into the page), face your palm in the direction of the velocity (to the left) and your thumb will point in the direction of motion of the –ve charges : toward a.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 3If the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing OUT OF the page)
va
dc
b
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 3 AnswerIf the wire was moved in the directionof the arrow, what would happen to the charges in the wire?
Electricity Generation
A. +ve charges pushed to a, -ve charges pushed to b.
B. +ve charges pushed to b, -ve charges pushed to a.
C. +ve charges pushed to c, -ve charges pushed to d.
D. +ve charges pushed to d, -ve charges pushed to c.
E. Nothing
Uniform B field (pointing OUT OF the page)
va
dc
b
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 3 ExplanationElectricity
Generation
Uniform B field (pointing OUT OF the page)
va
dc
b
Here, we see that the velocity is perpendicular to the magnetic field. We know therefore, that there will be a force that pushes the –ve charges in a direction perpendicular to BOTH the velocity AND the magnetic field – either toward a or toward b. To determine which of the two directions, use the right hand rule: point your fingers in the direction of the field (into the page), face your palm in the direction of the velocity (to the left) and your thumb will point in the direction of motion of the –ve charges : toward b.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 4Which of the following will NOT light upthe bulb?
Electricity Generation
A. Option AB. Option BC. Option CD. Option D.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 4 AnswerWhich of the following will NOT light upthe bulb?
Electricity Generation
A. Option AB. Option BC. Option CD. Option D.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 4 ExplanationElectricity
Generation
In situation C, the wires are moving but the + charges in each wire will be pushed outward (radially), so no electricity will flow around the loop.
In situation D, all the charges in the top half will be pushed down, and all the charges in the bottom half will be pushed up. These pushes will just cancel out, and again nothing will flow around the loop.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 5Which of these will light the bulbmost strongly?
Electricity Generation
A. Option AB. Option BC. Option CD. Option D.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 5 SolutionWhich of these will light the bulbmost strongly?
Electricity Generation
A. Option AB. Option BC. Option CD. Option D.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
Question 5 ExplanationElectricity
Generation
Situation B will light the bulb most strongly:We get the best results when one side of the loop is in a field Upwards, and the other side is in a field Downwards. This way the pushes on the charges push in the same direction AROUND the loop.
Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia
More Information: The right hand rule
Electricity Generation
More information on the right hand rule used to answer the previous questions can be found on the Hypherphysics site:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html