1.) A 500 turn circular coil with an area of 0.05 m2 is mounted on a rotating fr

Question

1.) A 500 turn circular coil with an area of 0.05 m2
is mounted on a rotating frame which turns at a rate of 20
rad/s in the presence of a 0.05 T uniform magnetic field which is perpendicular to the axis of rotation.
What is the instantaneous emf in the coil at the moment that the normal to its plane is parallel to the field?

________________________________________________________________________________________

2.)  An electron moves through a region of crossed electric and magnetic fields. The electric field E = 1000 V/m
and is directed straight down. The magnetic field B = 0.4 T and is directed to the left. For what velocity v
of the electron into the paper will the electric force exactly cancel the magnetic force?

Explanation / Answer

1.

Determine the time using 20 rad/s. You want the time when the normal is at 90 degrees to the field and the field is 90 degrees (perpendicular) to the coil, so that is at 180 degrees or 1 radians.
(This part is easier to visualize if you draw it out and image the motion of rotation through the field with regards to the normal)

1 rad / 20 rad /s = 0.05 seconds

N = 500
B = 0.05
A = 0.05
t = 0.05

emf = (500*0.05*0.05) / 0.025 = 1.25 / 0.05 = 25 Volts

2.

Since the electron is not deflected, the two forces are equal

E*q = q*v*B

so v = E/B = 1000/0.60 = 2500 m/s

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

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