Answer: 127.7 MHz.
- A 12.77 MHz
- B 63.87 MHz
- C 127.7 MHz
- D 637 MHz
Correct answer: C. 127.7 MHz
Explanation: Larmor frequency f = gamma x B/(2pi) where gamma_H = 2.675 x 10<sup>8</sup> rad/(T s). f = 2.675x10<sup>8</sup> x 3/(2pi) = 127.7 MHz.
Magnetic field lines form closed loops: outside the bar magnet they run from the N pole to the S pole; inside, they continue from S back to N, so the lines never start or end anywhere.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.