Please answer all questions if you can! Multiple-Choice Homework Problem 18.2 A
ID: 1447249 • Letter: P
Question
Please answer all questions if you can!
Multiple-Choice Homework Problem 18.2 A non-zero magnetic field exists in some region of space. What can be deduced about the electric field in the region?
(a) There must be an electric field in the region.
(b) There may or may not be an electric field in the region.
(c) There cannot be an electric field in the region.
Multiple-Choice Homework Problem 18.3 A Gauss gun is a magnetic projectile launcher made of a finite solenoid. To evaluate the torque on the a Gauss gun due to the earth’s field, approximate the Gauss gun as flat coil (all the loops in a plane) with 500 turns, radius 1.5cm, and carrying current 300A. The earth’s magnetic field is about 4 × 105T. Calculate the maximum torque exerted on the gun by the earth’s magnetic field.
(a) Maximum torque 1.7 × 105Nm.
(b) Maximum torque 0.0042Nm.
(c) Maximum torque 0.077Nm.
(d) Maximum torque 0.282Nm.
(e) Maximum torque 1.44Nm
Multiple-Choice Homework Problem 18.8 A rail gun is constructed of two parallel rails of length 1.75m and distance 3cm apart (center-to-center). Use the field of an infinite straight wire to approximate the field of the rails. If 100, 000A flows in the rail gun, compute the force one rail exerts on the other.
(a) 8.5N
(b) 58, 000N
(c) 120, 000N
(d) 175N
(e) 1.4 × 107N
Explanation / Answer
1) (b) There may or may not be an electric field in the region.
If the magnetic field varies, there will be electric field.
2) (b) Maximum torque 0.0042Nm.
maximum torque, Tmax = N*I*A*B*sin(90)
= 500*300*pi*0.015^2*4*10^-5
= 0.0042 N.m
3) (c) 120, 000N
force between the parallel wires, F = mue*I1*I2*L/(2*pi*d)
= 4*pi*10^-7*10^5*10^5*1.75/(2*pi*0.03)
= 116666 N
aproximately 120000 N