# V-I characteristics of Lamp

Aim:-    Aim  of the experiment to study V-I characteristics of an index scan lamp.

Apparatus Required:-

 S. No. Name of Equipment Type Range Quantity 1. Incandescant  lamp - 200 W 1 2. Voltmeter PMMC 1 3. Ammeter PMMC 1 4. Rheostat Tube Type 128ohm, 2.5Amp 1

Theory:- There is a practical no change in the resistance value in case of some alloys used in electrical works like manganin for a considerable variation of temperature in general for alloys the increase in resistance is very slight with increase in temperature for all pure metal like copper aluminum etc the resistance increase with an increase in temperature the resistance of such conducting materials at working temperature of tea degree Celsius can be found out by using equations given below

Resistance at   t0C,Rt=R0(1+αt)

Where R0=Resistance at 00C

α = temperature coefficient of the conducting material

however the resistance of carbon and electros decreases with increase in temperature to these are also the conducting materials their temperature coefficient Alpha is said to be negative the resistance of all insulating material sharping decrease with increase in temperature.

Circuit diagram:- the aim of experiment is to study the variation of resistance with rise in temperature the resistance of the filament of in descant lamp tungsten increase with rise in temperature as such a bulb has been chosen for this experiment the temperature of the filament depends upon the heat which it turns depends upon we square by R where we is the voltage applied across the filament of the bulb and R is your assistance does by applying different voltage to the filament of the bulb different amount of heat can be produced and different temperature can be obtained.

Procedure:-

1.      Connect the circuit as shown in the diagram with the switch bracket as slash W is in off position.

2.      Switch on DC supply close this which and very the rheostat to obtain different voltage and current values. note the voltage and corresponding current values. Record the calculate percentage error.

3.      Switch off supply then open the switch.

Observation Table:-

 Sr. No. Vin(Volts) Iin(Amp) R=v/I 1 20 0.22 90.90 2 40 0.28 142.86 3 60 0.34 176.47 4 80 0.40 200.00 5 100 0.46 217.39 6 120 0.50 240.00 7 140 0.34 259.26

Least count of Voltmeter = 4V

Least count of Ammeter = 0.02 amp

Remark:-The characteristic is non linear.

Precautions:-

1.      Make the connections properly.

2.      Note the reading of voltmeter and ammeter properly.

3.      Remove insulation from the connecting wire so that the current will flow properly.