Solution: R=E? 1I-r，

According to mathematical knowledge, the slope of R- 1I image is equal to e, and the absolute value of vertical axis intercept is equal to r,

So the electromotive force of the power supply is E=8? (? 0.9)3=3.0V，

Internal resistance r = 1ω

So the answer is: (1) 3 (2) 1.