When the deflection angle of the pointer is large, the battery anode in the ohmmeter is connected with the diode anode, and the black stylus is connected with the diode anode. Take the resistance R 0 as the internal resistance of the power supply, and draw the volt-ampere characteristic curve of the power supply in Figure A, as shown in the figure. The product of the vertical and horizontal coordinate values (0.8V, 12mA) at the intersection of two graphs is equal to the power consumed by the diode, and p = UI = 1× 10-2 W.