1. Two parallel conductors each of 0.5 m length, separated by 0.005 m and carrying 3.0 A in opposite directions, will experience what type and magnitude of mutual force?
ans: repulsive, 1.8 x10-4 N; force = L*(mu)*I1*I2/2*pi*d.
2. A current carrying wire of length 50 cm is positioned perpendicular to a uniform magnetic field. If the current is 10.0 A and it is determined that there is a resultant force of 3.0 N on the wire due to the interaction of the current and field, what is the magnetic field strength?
ans: 0.6 T; use f = B*I*L.
3. Superconductors can carry very large currents with no resistance. If a superconducting wire is formed into a solenoid of length 50 cm with 500 turns, what is the magnetic field inside the solenoid when the current is 104 A? (magnetic permeability in empty space mo = 4p x10-7 T*m/A)
ans: 12.6 T; use B = (mu)*N*I/length.
4. An incredible amount of electrical energy passes down the funnel of a large tornado every second. Measurements taken in Oklahoma at a distance of 9 km from a large tornado showed an almost constant magnetic field of 1.5 x10-8 T associated with the tornado. What was the average current going down the funnel? (magnetic permeability in empty space mo= 4p x10-7 T*m/A)
ans: 675 A; use B = (mu)*I/2*pi*r.
5. A high-voltage powerline 20 m above the ground carries a current of 2000 A. What is the magnetic field due to the current directly underneath the powerline? (magnetic permeability in empty space mo= 4p x10-7 T*m/A)
ans: 20.0 mT; also use B = (mu)*I/2*pi*r.
6. A circular loop carrying a current of 2.0 A is oriented in a magnetic field of 3.5 T. The loop has an area of 0.12 m2 and is mounted on an axis, perpendicular to the magnetic field, which allows the loop to rotate. What is the torque on the loop when its plane is oriented at a 37 deg angle to the field?
ans: 0.67 N*m; use torque = B*I*A*sin(37 deg).