Two hikers are reading a compass under an overhead transmission line that is 6.0
ID: 1433384 • Letter: T
Question
Two hikers are reading a compass under an overhead transmission line that is 6.00 m above the ground and carries a current of 0.750 kA in a horizontal direction from north to south
A. Find the magnitude of the magnetic field at a point on the ground directly under the transmission line.
B. Where is the magnetic field directed at a point on the ground directly under the transmission line.
C. One hiker suggests that they walk 50.0 m away from the lines to avoid inaccurate compass readings due to the current. Considering that the earth's magnetic field is on the order of 5.00×105 T , is the current really a problem?
The current is a problem for accurate compass readings. The current is not a problem for accurate compass readings.Explanation / Answer
A. If r is the distance from hikers to nearest point on the T/L (= 6 m) and I the current, then the magnetic field strength at the hikers is I/(2 x pi x r) = 750/(2 x pi x 6) = 19.90 A/m.
However you seem to be requesting the flux density (units Tesla) which is obtained by multiplying the magnetic field strength by 4 x pi x 10^(-7) giving 24.9 x 10^-6 Tesla.
B. This field will be in a west to east direction.
C. This field strength is around the same as the earth's just under the line (3 compared to 5) so "yes", it would substantially affect the compass.
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