## Saturday, November 20, 2010

### Electromagnetic Induction

1. An electron enters a 4.0 T field with a velocity of 5.0 x 105 m/s perpendicular to the field. What is the radius of curvature of its path?

2. A conducting rod of 25 cm is pushed across a magnetic field along a U-shaped wire at a constant speed of 2.0 m/s. The field is directed away from the observer and is 4.00 T. A current of 8.00 A is induced in the circuit.
A conducting rod of 25 cm is pushed across a magnetic field along a U-shaped wire at a constant speed of 2.0 m/s.
a. What is the potential difference induced in the circuit?
b. What is the resistance of the circuit?
c. What is the force used to push the rod?
d. In what direction is current flowing in the rod?

3. A wire with a linear density of 1 g/cm moves horizontally to the north on a horizontal surface with a coefficient of friction 0.2. What are the magnitude and the direction of the smallest magnetic field that enables the wire to continue in this fashion?

4. An electron is accelerated from rest through a potential difference of 18 kV, and then passes through a 0.34-T magnetic field. Calculate the magnitude of the maximum magnetic force acting on the electron.

5. A 0.0017 T magnetic field and a 5.7 x 103 N/C electric field both point in the same direction. A positive 2.0-mC charge moves at a speed of 2.9 x 106 m/s perpendicular to both fields. Determine the magnitude of the net force on the charge.

6. What is the magnitude of the magnetic force on an electron moving 5.0 x 104 m/s perpendicular to a uniform magnetic field of .20T?

7. What speed would a proton need to orbit 1000 km above the Earth along the magnetic equator where the magnetic field intensity is 4.00x10-8 T?

8.

a. Find the magnetic flux density 3.1 mm away from a long straight wire carrying a 1.2 A current.

b. What force per meter would act on a long straight wire 3.1mm away from and parallel to the wire in part (a) and carrying a 4.5A current?
c. What force would act on a 37 μC charged particle 3.1mm from the wire in part (a) and moving away from the wire at 6.5 m/s?

9. Find the magnetic flux density in the center of a 4.0 cm long air-core solenoid made with 4900 turns of wire and carrying a 2.5A current.

10. Express the attenuation distance for a plane electromagnetic wave in a good conductor in terms of the conductivity σ, permeability μ0, and frequency ω.