1,Used to reveal the existence of the uniform magnetic field.
2,Magnetic electricity coil is a physics experiment apparatus

1, Composition:  5cm, 10cm of length Solenoids with the copper wire of dia 0.25mm , one PMMC of 1.0mm with scalemeter of 12cm length , and eight electricity double-screw bolt ends.

 2, Direction : Connect the regulated power supply with the solenoid post head,  and insert magnetic strength sensor into the inner bore of the solenoid at constant speed. The stable reading from the sensor which can reveal the existence of the uniform magnetic field.