Question

एक रियोस्टैट क्या है? iska एक उपयोग दो।

Answer 1

Rheostat is a variable resistance which is used in the circuit to control the current.Resistance can varied in a circuit without the interruption so as to control the current.


symbol of resistor

It is similar the potentiometer used in electronic circuitory.


The above figure represents a rheostat (left) with its equivalent circuit on right.Terminal A and B are used to connect the input which marks the entry point of current.Terminal C is the output point for the current through rheostat.A coil of resistive wire is wound on the ceramic core which is non metallic material.A sliding contact with upper part ceramic or any non metal and lower portion with metal contacts.The position of the sliding contact represents the resistance in the circuit.For example:If we consider a circuit with a voltage source, resistor and a ammeter connected in series with a bulb at output side.So we connect the input of rheostat to Terminal B and output is obtained at Terminal C.So if the sliding contact is at point Terminal B then it represents minimum resistance position as current has zero resistance.Resistance is directly proportional to length and inversly proportional to Area of Contact.So at first instance the length is small and area of contact is also small so current has no resistance due to which full supply voltage will be across the bulb.Now if the position of sliding contact is at terminal A, then the length increases as well as the area of contact i.e. Area of turns of wire covered also increases due to which full resistance of rheostat is applied across the input voltage and so the current through the rheostat will be of low magnitude and hence the bulb will glow dim.