As shown in the figure, in a horizontal uniform electric field, a small ball with a mass of m and a charge of q is tied with an insulated thin wire with a length of l, and the upper end of the wire is

As shown in the figure, in a horizontal uniform electric field, a small ball with a mass of m and a charge of q is tied with an insulated thin wire with a length of l, and the upper end of the wire is fixed. In the process of (1) ball from A to B, it is obtained by kinetic energy theorem:

mgLsin60 +qUAB=0，

Solution: uab =-3mgl2q;

(2) The potential difference between Ba is: UBA=-UAB=3mgL2q,

So the field strength: E=UBAL? Lcos60 = 3mgq

Answer: The potential difference UAB between (1)AB is-3mgl2q;

(2) The field strength of uniform electric field is 3mgq. ..