I am reposting this question as previous question was not answered correctly or

Question

I am reposting this question as previous question was not answered correctly or completely.

Figure 1 shows the path of an proton in a region of uniform magnetic field. The path consists of two straight sections, each between a pair of uniformly charged parallel plates, and two half circles. When the proton is outside the plates, it sees only a magnetic field which exerts a force on the proton to make it travel around a circle. When the proton is between the plates, it sees both an electric and magnetic field, which both exert forces on the proton that cancel, so the proton travels along a straight line. Assume that the length L shown in the figure is known.

a. Calculation: If it takes the electron a time ? to make one complete trip, what is the strength of the magnetic field? Please show/explain your work.

b. Conceptual: What direction must the uniform magnetic field point? Please explain.

c. Conceptual: Consider the top set of parallel plates. Which plate is positively charged? Please explain.

Explanation / Answer

Diameter of the circular path, = L
So Radius, = L/2

In Magnetic Field,
Centripetal Force is provided by the Magnetic Force.
q*v*B = m*v^2/r
q*B = (m*v)/(L/2) ------1


Now, Speed of proton, v = Total distance / time
Total Distance = 2*L + (*L)
time =

So, speed = (2*L + (*L))/

Substituting value in r ,
q*B = (m*(2*L + (*L))/*(L/2)
q*B = (2*m* (2 + ) )/
B = (2*m* (2 + ) )/ (*q)

(b)
Using Right hand thumb rule,
The direction of Magnetic Field is " Into the page."

(c)
In the top plate, Electric Force on the proton is Upwards , so Electric Field is also upwards.
This means. Lower plates is positively charged.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.