① Resistance box and ammeter are needed to measure electromotive force and internal resistance of power supply by impedance method. According to the meaning of the question, the internal resistance of the fruit battery is very large, and the maximum current through the fruit battery is very small. In order to ensure the safety and accuracy of measurement, ammeter B and sensitive ammeter A2 (range 0 ~ 0.6 Ma, internal resistance R2) can be selected.

Therefore, the experimental equipment is optional: BDE. ..

② The experimental circuit diagram of measuring electromotive force and internal resistance of power supply by impedance method is shown in the figure.

③ According to Ohm's Law of Closed Circuit:

E=I(r+R+R2)

Deformation: 1I= 1ER+r+R2E.

According to the mathematical relationship, the intercept of a straight line on the longitudinal axis is m=r+R2E,

The slope of the straight line is k= 1E,

Solution: E= 1k, r=mk-R2.

So the answer is: ① BDE;

② As shown in the figure:

③ 1k，mk-R2。