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Transcript
EXPERIMENT NO:2 OBJECTIVE: VERIFICATION OF NETWORK THEOREM i) ii) iii) SUPERPOSITION THEOREM THEVENIN THEOREM MAXIMAM POWER TRANSFER THEOREM APPARATUS REQUIRED: Sl Instrument no. type Range/specification Qty. 1. Supply Dc 0-12V 1 2. Experimental board Kit or Breadboard - 1 3. voltmeter MC (0-15)V 1 4. ammeter MC (0-10)mA 1 5. resistance 450Ω 1 6. resistance 350 Ω 1 7. resistance 250Ω 1 THEORY: In a linear network containing more than one energy sources, the current flow in any branch is the algebraic sum of currents due to each individual energy source. At the of consideration of one energy source, rest of the energy sources will have to be inactivated. To inactivate voltage source, voltage source will be replaced by internal resistance and if internal resistance is not given then voltage source will be short- circuited. To inactivate current source, current source will be replaced by internal resistance and if internal resistance is not given then current source will be open- circuited. CIRCUIT DIAGRAM: Figure(a) Figure(b) OBSERVATION TABLE: Sl no. Current “I” Current “I1” Current “I2” I=I1 + I2 Practically Practically Practically (Algebric Sum) Circuit diagram Fig (a) Fig (b) PROCEDURE: i) Short circuit the terminals E &F. ii) Connect the 9V supply with terminal DC. iii) Connect the ammeter in series with branch DC. iv) Observe the reading of ammeter “I1” v) Again Short circuit the terminals DC having an ammeter in series vi) Connect the 5V supply with terminal EF. vii) Observe the reading of ammeter “I2”. RESULT: The net current I is the algebraic sum of I1 & I2 due to the individual voltage source taking one at a time I=I1 + I2 PRECAUTION: i) Do not make interconnection on the board with mains switched ON. ii) As soon as mains is ON .the reading in the meters must be zero. If the reading in the meters is not zero, check the meters. iii) Keep the hands away from the mains transformer. iv) Both the power supplies are short circuit protected. ii) THEORY OF THEVENIN THEOREM: This theorem provides a mathematical technique for replacing a linear two terminal network by a voltage source in series with resistance Rth. According to Thevenin’s theorem “Any linear two terminal network, containing energy source and resistances, can be replaced by an equivalent circuit consisting of a voltage source Vth in series with resistance Rth”. The value of Vth is the open circuit voltage between the load terminals of the network and Rth is the equivalent resistance between the load terminals with all energy sources replaced by their internal resistance if internal resistances are not given then voltage source will be short circuit, while current source will be open circuit. Load current (IL) across the load resistance (RL) is given by the equation IL Vth ( Rth RL ) Where Vth=open ckt voltage across the terminals. Rth=equivalent resistance across the terminals. RL= the load resistance CIRCUIT DIAGRAM: To find Rth: To find Vth: Figure(a) To find IL: Figure(b) IL Vth ( Rth RL ) OBSERVATION TABLE: Sl no. VOC Vth Rth IL IL = Vth / Rth+ RL practically theortically computed measured calculated CALCULATION: IL Vth ( Rth RL ) ; RL=150Ω Vth= Rth= PROCEDURE: i) Connect the circuit. According to the fig (a) and find VOC ii) Connect the circuit. According to the fig(b);observe IL PRECAUTION: i) Do not make interconnection on the board with mains switched ON. ii) As soon as mains is ON .the reading in the meters must br zero. If the reading in the meters is not zero, check the meters . iii) Keep the hands away from the mains transformer. iv) Both the power supply are short ckt. Protected RESULT: We find that the calculated value of load curent “IL” is equal to the measured “IL” IL(calculated)= IL(measured) iii) MAXIMUM POWER TRANSFER THEOREM: THEORY: According to the maximum power transfer theorem as applied to DC network a resistance load will abstract maximum power from a network when the load resistance of the is equal To the resistance of the network as viewed from the output terminals with all energy source are replaced by their internal resistance. In the case of AC network load impedance should Be complex conjugate of source impedance. Po = Pmax. When RL=RT=RTH Pmax.= V2TH/ 4 RL And power delivered to the load resistance Po = I2L RL CIRCUIT DIAGRAM: CALCULATION: IL = Vth / Rth+ RL Vth= Rth= Pmax.= V2TH/ 4 RL OBSERVATION TABLE: Po = I2L RL in watt sl no. Vth Rth Pmax.= V2TH/ 4 RL For variable load theoritically computed theoritically RL=50Ω RL=100Ω RL=150Ω RL=200Ω PROCEDURE: i)Connect the ckt. According to the fig (a) ii) Find the load current IL1, IL2, IL1, ....... for the load resistance RL=50Ω,100Ω, 150Ω,........... PRECAUTION: i) Do not make interconnection on the board with mains switched ON. ii) As soon as mains is ON .the reading in the meters must br zero. if the reading in the meters is not zero,check the meters . iii) Keep the hands away from the mains transformer. iv) Both the power supply is short ckt. Protected RESULT: From the observation table we can observed that power delivered is maximum when the load resistance RL=RTH