Answer & Explanation:I need help with a physics lab worksheet. I have attached the worksheet below.
virtual_lab_29.doc
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Name
Date
Class
The Effect of an Electric
Field on Moving Charges
Lab 29: The Effect of an Electric Field on Moving
Charges
Problem
To investigate the effect of a static electric field on various moving charges
Background
As scientists first began investigating the properties of atoms, they discovered
that they could extract negatively charged particles. They called these particles
electrons. In order to understand the nature of these particles, scientists wanted
to know how much charge they carried and how much they weighed. J.J.
Thomson was a physics professor at the famous Cavendish Laboratory at
Cambridge University. In 1897, Thomson showed that if you could measure
how far a beam of electrons was bent in an electric field and in a magnetic field,
you could determine the charge-to-mass ratio (q/me) for the electrons. Knowing
this ratio, the individual charge and mass of an electron could be calculated.
Another particle ejected during nuclear decay is the alpha particle. An alpha
particle is a helium nucleus, that is, a helium atom without its two electrons. As
you will see, a beam of alpha particles can also be deflected by an electric field.
Skills Focus
Predicting, observing, drawing conclusions
Procedure
1. Start Virtual Physics and select Effect of an Electric Field on Moving Charges
from the list of assignments. The lab will open in the Quantum laboratory.
2. The experiment will be set up on the table. There is an electron gun on the
left side of the as the source. What type of charge do electrons have?
3. There is a phosphor screen on the right side of the table to detect the charged
particles. Turn on the phosphor screen by clicking on the green/red button.
What do you observe and what do you think that it shows?
The Effect of an Electric Field on Moving Charges
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.
ISBN 1-269-73240-4
92
Name
Date
Class
The Effect of an Electric
Field on Moving Charges
4. Drag the lab window down and left and the phosphor screen window up
and right in order to minimize the overlap. Push the Grid button on the
phosphor screen. Click once above the ones place on the Electric Field
modifier meter near the center of the table. Observe the spot. Click a few
more times above the ones place on the Electric Field, until the field is at 5V.
(If you mistakenly click between digits, it will move the decimal point. To
move the decimal point back again, click where it was originally.) What
happens to the spot from the electron gun on the phosphor screen?
5. Predicting What do you think would happen to the spot if you increased
the voltage of the electrons leaving the electron gun? Why?
6. Observing Increase the voltage of the source by clicking above the
hundreds place on the electron gun voltage controller (the second meter
from the left). You are not changing the number of electrons leaving the gun,
just giving each of them greater electrical potential energy. What happens to
the spot on the phosphor screen? Why does this happen?
7. Predicting What do you think would happen to the spot now if you
increased the voltage on the Electric Field modifier that the electron beam is
passing through? Why?
8. Test your prediction, then zero out the Electric Field meter by clicking on the
appropriate digit buttons until the spot on the phosphor screen is once again
centered.
ISBN 1-269-73240-4
9. Double-click or click and drag the electron gun to move it to the Stockroom
counter. Enter the Stockroom by clicking inside it. Double-click the electron
gun to move it back to the shelf. Double-click on the alpha source to select it
and move it to the Stockroom counter. Click on the green Return to Lab arrow
to return to the lab. Drag the alpha source from the Stockroom counter and
place it on the table where the electron gun was originally placed (the middle
spotlight). Click on the front of the alpha source to open the shutter. What
appears on the phosphor screen? What charge do alpha particles have?
The Effect of an Electric Field on Moving Charges
93
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.
The Effect of an Electric
Field on Moving Charges
Name
Date
Class
10. Change the unit for the Electric Field from V (volts) to kV (kilovolts) by
clicking once above the unit. This electric field is one thousand times
stronger than what you used previously for the electron gun. Observe the
spot as you increase the Electric Field strength from 0 kV to 5 kV. The
movement is slight so pay careful attention. Which direction did the spot
move when you increased the electric field?
How does this direction of movement compare with the direction of
movement for the electron beam in the electric field?
11. Drawing Conclusions Why do you think that it takes a significantly
stronger electric field strength to move the beam of alpha particles
compared to the beam of electrons?
The Effect of an Electric Field on Moving Charges
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.
ISBN 1-269-73240-4
94
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