Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.
A current runs from West to East in a wire, creating a magnetic field around the wire.
Question 1: In the space above the wire, the magnetic field points in which direction?
Answer: South
Question 2: The strength of the magnetic field at a distance of 1 m from the wire is 1 microTesla . At a distance of 2 m from the wire, the strength of the magnetic field is
Answer: 0.5 microTesla: the magnetic field strength around a
long wire drops as 1/r (not 1/r^2)
Question 3: What is the size of the current running through the wire, in Amps?
Answer: The strength of the magnetic field B at a distance r from
a wire carrying a current I is
mu * I
B = ----------
2 * pi * r
so we can turn it around to find the current:
2 * pi * r * B
I = ---------------
mu
= 2 * pi * (1 m) * (1 x 10^(-6) Tesla)
-----------------------------------
4 * pi * 10^(-7) Tesla*m/Amp
= 5 Amps
Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.