For laboratory use as a variable series resistance or as a potentiometer. Can control current and voltage. Made from heat resistant, air cooled, hollow porcelain tube closely wound with a resistance wire of copper nickel alloy which is previously oxidised to provide perfect insulation. The end supports are made of metal with provision for screw mounting. A bakelite slider carries a phosphor bronze contact which can be moved rapidly and smoothly and can rest anywhere along the winding. The insulation is sand-papered off where the slider makes contact. Resistance in ohms and current carrying capacities are engraved on contact carriage. Three terminals are provided for electrical connections, one at each end of the winding and the third at one end of the slide rod so that the unit can be used either as a rheostat or as a potentiometer. Available with a variety of resistances and current carrying capacities. Power ratings (watts) can be calculated as Watts = (Current in amperes)2 x Resistance in ohms |
