1. For illustration of the structure and the Principls about sliding rheostat. 2. Used for adjusting the current intensity infinitely while experimenting and obtain different voltages from the power supply. Resistance: 100 Om Max. current: 0.6 A 3. structure seramic tube 1.on which winded with contantanwire coated by a oxidazed insulating layer AT two ends of the contantan resistant wite are mounted with two connectors 2. Above the resistant tube a metal sliding bar equiped with a moving block 4. below which there are two contacotrs 5. ensuring googd contact with tesistant wire At the two ends of slidng Bat mounted with two connectors 6. sliding bat and the ceramic tube are supported and fixed by two trestles.