(1) The resistance measured by the ohmmeter is equal to the reading multiplied by the magnification. When measuring with ×1k, the deflection angle of the pointer is too large, and the measurement error is large. It is more accurate to measure with × 100, so r =18×100ω =188.

(2) In order to accurately measure the resistance value, the voltage in the circuit needs to have a large range of change, and the resistance value of the sliding rheostat is much smaller than the measured resistance, so the sliding rheostat should be connected by voltage division;

And because RVR =10×1031800 ≈ 5.6 and RRA= 180050=36, rvr.