Physics 2145 Test 3 Preparation Homework
1. Two long wires, perpendicular to the page,
each carry a current of I = 5.25 A in the
directions shown in the diagram.
a) Show the direction of the magnetic field at
point P, due to the current in the lower wire.
b) Calculate the magnitude of the magnetic
field at point P due to the current in the lower
wire.
5cm
5cm
P
5cm
c) Do parts a and b for the upper wire.
d) Sketch the total magnetic field at P due to
the current in both wires.
e) Calculate the total magnetic field at point P.
f) Show the direction of the force the magnetic field of the lower wire exerts on the upper wire.
2. A particle of mass m, charge +e, and velocity v passes
straight through a velocity filter as shown. The
magnitude of the electric field between the two plane
parallel plates is E.
++++++++++++++++++++++
v
a) In what direction is the magnetic field needed?
b) In terms of v and E, what is the magnitude of the need
magnetic field, B?
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c) What magnetic field would be required if the charge
on the particle were -2e, with the same mass and velocity? (Give direction and magnitude.)
3. In a mass spectrometer, particles with a charge of +e are sent into the spectrometer with a velocity
2.50× 105 m/s. They are found to move in a circle with a radius of 0.215 m. The magnetic field has a
magnitude of 0.050 T. What is the mass of the particles?
5. A loop of radius 5.00 cm carries a current of 240 mA and is in a uniform magnetic field of 0.625 T.
250
B
a) What is the torque on the loop?
b) On the drawing, sketch the orientation of the loop when the torque on the loop is a maximum.
c) What is the magnetic flux through the loop?
5. The loop shown has a diameter of 10 cm and a resistance of 0.10 Ω. The
magnetic field is perpendicular to the page and has the direction shown and is
increasing at a rate of 0.50 T/s.
Indicate on the diagram the direction of the current induced in the ring.
What is the magnitude of the induced current?
6. A horizontal slide wire of mass m and length L is constrained to move
up and down without friction as it remains in contact with a vertical
conducting frame, as shown. The resistance of the frame is negligible.
The entire apparatus is in an external uniform magnetic field B directed
into the page.
a) The slide wire is released from rest. What is the direction of the
induced current?
b) Calculate the induced emf when the wire has a speed v.
c) What is the direction of the magnetic force on the wire?
d) Find the resistance R of the wire for which the wire reaches a constant
speed vf (Hint: constant speed requires zero net force).
frame
B
g
m
slide wire
L