(2006? Because the electrons of Huai 'an mode 2 are stationary, they have been accelerated by the electric field between M plate and N plate (the voltage between the two plates is U), and then injected from point A perpendicular to the magnetic field boundary. The velocity of electrons accelerating between m and n is v, which is obtained by kinetic energy theorem:

12mv 2-0 = EU

After the electrons enter the magnetic field, they make uniform circular motion, and let its radius be r, then:

evB=mv2r

The trajectory of electrons in the magnetic field is as shown in the figure, similar to a triangle.

L 12L2+d2=L2+d2r

It is obtained from the above three formulas: B=2LL2+d22mue.

Answer: The magnetic induction intensity of uniform magnetic field is 2LL 2+D 22MUE.