Certain bacteria (such as Aquaspirillum magnetotacticum) tend to swim towards th
ID: 1281480 • Letter: C
Question
Certain bacteria (such as Aquaspirillum magnetotacticum) tend to swim towards the earth's geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. If a transmission line carrying 100 A is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (Assume that a field less than 5.0% of the earth's field would have little effect on the bacteria. Take the earth's field to be 5.0*10^-5 T and ignore the effects of the seawater).
Explanation / Answer
Minimum Magnetic field Strength
Bmin=5%*Bearth
Bmin=(5/100)*(5*10-5)=2.5*10-6 T
Magentic field due to current carrying wire
B=uo*I/2pir
=>r=uo*I /2piB=/(4pi*10-7)*100/2pi*(2.5*10-6)
r=8 m