Review - Chapters 30 -32

  1. A conducting ring is suspended by 2 insulated strings as shown. The ring has a circumference of 35cm. When the magnet is located at point A, the B field at the ring is 0.2 mT in strength. The magnet is moved to point C over a 1 ms interval and the B field increases at a steady rate to 0.65 mT.

SN

pt. A pt. C

  1. Find the induced emf in the ring.
  2. Assume the ring has rectangular cross section of 1cm X 1mm and is made completely of aluminum (p = 2.75E-8 Ωm). Determine the magnitude of the induced current.
  3. What is the direction of the induced current (clockwise or counterclockwise) ?
  4. If the magnet were pulled back from pt. C to pt. A, what would happen to the direction of the induced current?
  1. A large solenoid of 200 turns is 5 cm in length and carries 45 mA of current. A square loop of wire, side 2mm, is looped 50 times inside the solenoid. What is the induced emf in the wire if the current in the solenoid is reduced to 0 amps at a steady rate in 0.005 seconds?
  1. A large solenoid of radius 15 cm has 500turns/cm and carries 0.1 A of current. A smaller solenoid of radius 5 cm and 500 turns/cm is placed inside.
  2. Determine the B field created by the large solenoid.
  3. What is the induced emf in the smaller solenoid.?
  4. What is the magnitude of the current in the smaller solenoid if it has resistance of 2E-3Ω?

4. N

WE

S

The top wire has 2 C/S of electron movement and the bottom wire has 5 C/S of electron movement.The wires are each 58 cm in length and separated by a distance of 3 mm. An electron is placed just in the middle of the wires.

  1. Determine the magnitude and direction of the B field in the center of the wires.
  2. Determine where the B field is zero.
  3. Determine the force (magnitude and direction) on the electron.
  4. What is the force (magnitude and direction) on the top wire?
  1. Using ampere’s law, derive the expression for the B field of a solenoid’
  2. Inside
  3. Outside

6. xxxx

xxxx B field

xxxx

xxxx

xxxx

An electron is traveling East at 2E4 m/s as it enters an external B field of strength 117 mT and direction as shown.

  1. What is the radius of the circular path that the electron takes?
  2. What is the direction of the force on the electron JUST as it enters the B field?

7. A conducting bar (l=0.2m) is pulled across conducting rails at a constant velocity of 4m/s.

x x x x x x x

Rx x x x x x x

Assume the magnetic field has a strength of 0.3 T, and the total resistance of the circuit is 0.008 Ω.

  1. Determine the induced emf in the circuit.
  2. Determine the magnitude and direction of the induced current.
  3. Determine the power dissipated in the resistor
  4. What is the magnitude and direction of the force acting on the induced current in the bar?
  1. Determine the flux of through a circular loop of wire with a diameter of 4 cm that experiences a constant B field of 40 mT.
  1. If the magnetic flux of a 20 turn square loop of wire is given as a function of time by:

Φ = 10t2 -3t Webers, determine the induced emf of the wire loop at 5 seconds.

  1. Determine an expression for the B field (magnitude and direction) at point P below.

All wires are carrying a current, i. All answers must be in terms of i, x and constant values.

X x

x

P