Question

Assertion: A liquid rheostat is a type of variable resistor, which may be used as a dummy load or as a starting resistor for large slip ring motors.
Reason: The salt water rheostat operates at unity power factor and presents a resistance with negligible series inductance compared to a wire wound equivalent.
A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C) Assertion is correct but the reason is incorrect.
D) Both assertion and reason are incorrect.

Answer 1

Hint: A liquid rheostat is a changeable resistor in the form of a liquid rheostat. This may be used as a starting resistor for big slip ring motors or as a fake load. It consists of a tank filled with brine or another electrolyte solution, into which electrodes are submerged to produce an electrical load. To enhance or reduce the electrical resistance of the load, the electrodes can be elevated or lowered into the liquid. The mixture must not boil in order to keep the burden stable.

Complete answer:
A liquid rheostat is a changeable resistor that may be used as a dummy load or to start huge slip ring motors.
It consists of a tank holding brine or another electrolyte solution in which electrodes are submerged to produce an electrical load in its most basic form. To decrease or increase the electrical resistance of the load, the electrodes can be elevated or lowered into the liquid.
When compared to a wire wrapped counterpart, the salt water rheostat runs at unity power factor and shows a resistance with negligible series inductance. It was frequently employed by generator assemblers.
Fixed electrolyte resistors are used to ground the neutral in high-voltage distribution networks to provide current limiting action and keep the voltage across the ground at a safe level during a failure. The liquid resistor, unlike a solid resistor, self-heals when it is overloaded. The resistance is usually set at commissioning and then fixed. Modern motor starters are completely enclosed, and electrode movement is controlled by a servo motor. A 1 tonne tank will often start a 1 megawatt slip ring type motor, however start times vary greatly depending on the application.
We can conclude that both Assertion and Reason are correct and Reason is the correct explanation for Assertion. Hence option (A) is correct

Note:
Stainless steel electrodes and sodium carbonate or other salts are used in modern designs, and the container is not used as an electrode. The electrodes are fixed in some systems, and the liquid is lifted and lowered using an external cylinder or pump. Water circulation to external heat exchangers may be employed in motor start systems used for frequent and quick starts and restarts, resulting in a significant heat load on the rheostats. In such circumstances, anti-freeze and anti-corrosion additives must be carefully chosen so that resistance does not deteriorate or algae or bacteria proliferate.