Focus on Concepts, Incorrect. Right-Hand Rule No. 2 (Section 21.7) indicates tha
ID: 1491190 • Letter: F
Question
Focus on Concepts, Incorrect. Right-Hand Rule No. 2 (Section 21.7) indicates that the magnetic fields from both wires in 3 point into the screen, away from the reader. Thus, the net magnetic field cannot be zero. The drawing shows four situations in which two very long wires are carrying the same current, although the direction of the currents may be different. The point P in the drawings is equidistant from each wire. Which one (or more) of these situations gives rise to a zero net magnetic field at P? 2 and 4 3 and 4 Only 1 2 and 3 Only 2Explanation / Answer
The correct choice is
Case 2 and 4
In case 2 :
using right hand rule , the magnetic field by wire above point P is in inward direction and the magnetic field by the wire below point P is in outward direction. since each wire has same current and are equidistance from point P , the magnitude of magnetic field by each wire is same.
Since the magnetic field by two wires are equal in magnitude and opposite in direction , net magnetic field at P becomes 0.
Case 4 :
using right hand rule , the magnetic field by wire above point P is in inward direction and the magnetic field by the wire on right of point P is in outward direction. since each wire has same current and are equidistance from point P , the magnitude of magnetic field by each wire is same.
Since the magnetic field by two wires are equal in magnitude and opposite in direction , net magnetic field at P becomes 0.