A short bar magnet of moment 0.4 A m 2 gives an axial (end-on) field at 0.2 m of ( 0 /4 = 10 -7 ):

A short bar magnet of moment 0.4 A m 2 gives an axial (end-on)…

Answer: 1 10 -5 T.

A 2.5 × 10-6 T
B 5 × 10-6 T
C 1 × 10-5 T
D 2 × 10-5 T

Correct answer: C. 1 × 10-5 T

Explanation: Baxial = (μ0/4π)(2m/r3) = 10-7 × (2 × 0.4)/(0.2)3 = 10-7 × 0.8/0.008 = 1 × 10-5 T.

Magnetic field lines of a bar magnet, emerging from the north pole and curving round to enter the south pole outside the magnet

Magnetic field of a bar magnet: field lines emerge from the north pole and re-enter at the south pole outside the magnet, forming continuous closed loops. Image: Geek3, CC BY-SA 3.0, via Wikimedia Commons.

Concept context

Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.

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A short bar magnet of moment 0.4 A m<sup>2</sup> gives an axial (end-on) field at 0.2 m of (&mu;<sub>0</sub>/4&pi; = 10<sup>-7</sup>):

Concept context

More Magnetism and Matter questions

A short bar magnet of moment 0.4 A m<sup>2</sup> gives an axial (end-on) field at 0.2 m of (μ<sub>0</sub>/4π = 10<sup>-7</sup>):