Question

1. What do the positive helium ions do for the e / m apparatus? Choose the most complete, best answer.

1. They help focus the electron beam and they emit photons which allow the beam to be seen.
2. They help focus the electron beam.
3. They emit photons which allow the beam to be seen.
4. They get hot and glow.
5. They are there so that the bulb does not implod
6. They are there only when the electrons are not orbiting, otherwise, they move to the outer edge of the bulb.

2. When is a charge acted upon by a magnetic force?
   1. When the charge moves within a magnetic field.
   2. When the charge is close enough to the magnetic field to feel it.
   3. When the charge is negative.
   4. When the charge is positive.
   5. Never, charges respond only to electric fields
   6. When the chage is close enough AND stationary.
3. According to equation (4) in the manual, the magnetic field is constant if given a coil and constant current.
   1. True
   2. False
4. Given a current of 1.3 A; a coil radius of 0.13 m; and N=130, then what is the strength of the magnetic field in milliTeslas? (Use three sig figs. or write N/A if there is not enough information.)

Let's say that you are given a magnetic field

B = 0.0015 Teslas.

5. You also have an average V / d 2 = 27,287 V/m 2;

what is the value for e / m ?

units are suppressed

(Report your answer with three sig. figs. and use scientific notation "E". ie. 1.98E11)

6. What are the units of the last answer?
   1. [C / kg]
   2. [kg / C]
   3. [C]
   4. [kg]
   5. [T]
   6. [mT]
   7. None of these
7. Should we include the force of gravity in our error analysis? (After all, gravity does affect the electrons.)
   1. Yes
   2. No
8. You are looking at the cross section of a coil. The conventional current is traveling clockwise. Which way is the magnetic field traveling?
   1. Into the coil (away from you).
   2. Out of the coil (towards you)
   3. There will be no field because there is no moving charge.
   4. More information is needed within the question
9. According to the manual, what is the angle between the magnetic field and the velocity of the electron?
   1. 90 degrees
   2. 45 degrees
   3. 180 degrees
   4. 30 degrees
   5. 2π radians
   6. 3 π / 2 radians
   7. All of these because it depends on where the electron is at the time.
10. What is the accepted value for e/m?

Use Scientific Notation (i.e. 1.76E11)

answer in C/kg

Answer 1

1) (a)They help focus the electron beam and they emit photons which allow the beam to be seen.

2) (a)When the charge moves within a magnetic field.

Magnetic force is:

F = qvB

So, if v = 0, no magnetic force is there.

3) True

4) B = u₀NI/2R

= (4pi*10^-7)(130)(1.3)/(2*0.13)

= 8.17*10^-4 T

Please post the other questions separately. Thanks and good luck :)