Abstract: The magnetic sensor ( electronic compass) in the smartphone is used to study the magnetic simple

pendulum based on the Phyphox APP. The results showed that the behavior of magnetic induction with time varies

with different amplitude angles. Only when the amplitude angle is less than 1°，the simple harmonic vibration of the

simple pendulum could occur. The curve of magnetic induction via time at different amplitude angles can be described

by magnetic dipole model combined with large angle pendulum formula. The local gravity acceleration measured

by the smartphone magnetic sensor is 9.868 m/s2 . Due to the small air damping of the magnetic pendulum，the

experimental error is only 0.8%.

Key words: simple pendulum, Phyphox, smartphone, magnetic dipole, air damping