question_answer 19)

A telephone cable at a place has four long straight horizontal wires carrying a current of 1.0 A in the same direction east to west. The earth's magnetic field at the place is 0.39 G, and the angle of dip is . The magnetic declination is nearly zero. What are the resultant magnetic fields at points 4.0 cm below the cable?  

Answer:

Using                                 and                 Magnetic field produced by telephone cable (4 wires)                                                 Field below the cable                                                 Resultant field,                                                                 with angle                 Field above the cable                                                 Resultant field,                                                                 with angle .