EXPERIMENT NO.1

NAME: Verification of Kirchoff’s current law.

Object: To justify the law’s by experimental result of a linear resistive network.

Theory: It states that in any electrical network, the algebraic sum of currents meeting at node of a circuit is zero.

Apparatus required:

S.No. Items Range Number

Circuit diagram:

Procedure:

1. Connect the circuit diagram as shown in figure.2. Adjust the supply voltage so all the instruments give reading within their range.3. Note down the voltage V1, V2and Vs and i1,i2,i3.

Observation:

S. No. Vs V1 V2 i1 i2 i3 V1+V2 i2+i3 %Error

Calculation:

Result:

Precautions:

1. Initially all the rheostats should be set in middle.2. Supply varic should be on zero.3. The connections should be tight.4. Voltmeter and ammeter should be of proper range.

QUES: Write the kirchoff’s current law.

QUES: What do you mean by % error?

Experiment no.2

Name: Verification of kirchoff’s voltage law.

Object: To justify the law’s by experimental result of a linear resistive network.

Theory: It states that the algebraic sum of voltages in any closed path in a network, traversed in a single direction is zero.

Apparatus required:

S. No. Items Range Number

Circuit diagram:

Procedure :

1. Connect the circuit diagram as shown in figure.2. Adjust the supply voltage so all the instruments give reading within teir range.3. Note down the voltage V1,V2 Vs and i1,i2,i3.

Observation:

S. No. Vs V1 V2 i1 i2 i3 V1+V2 i2+i3 %error

Calculation :

Result :

Precautions:

1. The connections should be tight.2. The voltmeter and ammeter should be of proper rating.

QUES: Write the kirchoff’s voltage law.

QUES: What do you mean by % error?

Experiment no.3

Name : Verification of maximum power theorem.

Theory: A resistive load abstract maximum power from a network when the load resistive equals the internal resistance of the network as viewed from the output terminals, with all energy sources removed, leaving behind their internal resistances.

Apparatus required:

S. No. Item Range Number

Circuit diagram:

Procedure :

1. Connect the circuit as shown in figure.2. Adjust the voltage supply so that all the reading within their range.3. Fix the value of supply and sources resistance. Note down the voltage across and

current through Rs. iL by ammeter reading. Calculate the value of Rs.4. Vary the load resistance RL, measure the voltage across the load resistance RL and

current through RL. Calculate the RL take different reading of RL so that some value must be higher than Rs so that in the graph of delivered power point is observable.

Observation :

Reading of supply voltage Vs =………………….volt

S. No. Voltage across Rs

Current through RL

Voltage across Rs

Value of source resistance

Value of load resistance

Power delivered to load resistance.

v iL VL Rs=V/IL RL=VL/iL P=i²rl

Calculation:

Result: A graph is plotted between load resistance RL and power delivered to RL.

From the graph it is clear that RL=RsMaximum power transfer theorem is proved.

Precautions : 1. Make the circuit as per the circuit diagram.2. Make all the connections carefully.3. Do not exceed the supply voltage more than the range of working equipments.

QUES: Write the maximum power transfer theorem?QUES: At which efficiency the maximum power occurs?

Experiment no.4Name: Verification of Thevenin theorem.

Theory: According to Thevenin theorem, any linear bilateral active network across any two terminals can be replaced by a voltage source and a resistance where voltage source is equal to open circuit voltage across terminals and resistance is equal resistance across terminal on replacing sources by their internal resistance.

Apparatus required:

S. No. Item Range Number

Circuit diagram:

Procedure:1. Connect the circuit as shown in figure1.fIx R1, R2, R3 and Vs(source voltage

approximately upto 60% volt) by varying the load resistance RL. Note down VL,iL and calculate the value of r1.

2. By removing load resistance and ammeter as in fig.2 take the open circuit voltage i.e. Vth

3. Remove the source voltage and then short circuit r1 and r3 terminal as in fig3 and apply the voltage between A&B. Taking the reading of voltmeter and ammeter. Calculate thevenin’s resistance i.e. Rth=v/i.

Observation:

S.No.

Source voltage

Current through load resistance

Voltage load resistance

Value of load resistance

Thevenin voltage

Thevenin’s resistance

Current through load resistance by thevenin equip. circuit

Vs iL VL RL=VL/iL Vs Rth=v/i ith=Vth/(Rth+r)RL

Calculation:1. Calculate value of load resistance from.2. Calculate thevenin’s resistance Rth.3. Calculate the current through load resistance.

Result: iL(measured).

QUES: Write the thevenin theorem?QUES: What are the limitations of thevenin theorem?

Experiment no.5NAME: Computation Of equivalent resistance.

Object: To compute the equivalent resistance of a given combination of resistance and verify the result experimentally.

Theory: Equivalent resistance of between the a & b can be calculated as Req(calculated) =r1+r2+r3/(r2+r3).experimentally it can be measured by voltmeter-ammeter method, by measuring voltage v and current i1 as : Req(measured) = V/i1 percentage value of r1,r2, r3 can be determined by measuring voltage and current in these resistance, as: R1 =V1/i1, R2 = v2/i2, R3 = V3/i3

Apparatus used:

S.No. Name of item Range Numbers

Circuit diagram:

Procedure: 1. Connect the diagram as shown in figure.2. Switch on the supply.3. Make suitable adjustments so that all the meters show their reading within their scale

ranges.4. Note down the reading of all the measuring instruments.5. Calculate Req(measured)= v/i1, r1 = v1/i1, r2 = v2/i2 and Req(calculated)

=R1+R2R3Rr2+R3).6. Calculate percentage error between Req(measured) and Req(calculated).

Observation:

S.No.

V V1 V2 i1 i2 i3 Req(mea)=V/I1

R1 R2 R3 Req(cal)=R1+R2R3/(R2+R3)

% Errror

Calculation :

Result: %Error between Req(mea) and Req(cal).

Precautions:1. Make the circuit as per the circuit diagram.2. Make all the connections carefully.3. Do not exceed the supply voltage more than the range of working equipments.

EXPERIMENT NO.6Name: Open circuit test on single phase transformer.

Objective: To find the no load current and no load losses of a single phase transformer vary with the applied voltage and to the no load parameters of the transformer.

Circuit diagram:

Specification of equipment:

S. No. Item Range Manufacturer Maker’s no.

Procedure:a) Connect as shown in the circuit diagram.b) The H.V. side is to be kept open and the supply is to be fed to the L.V. side through an

ammeter and a low power factor wattmeter from a variac.c) Note the name plate rating of the transformer and choose suitable rating of the meters.d) The variac output voltage is increased by 10v at step going upto 115% of the rated

voltage of the L.V. winding. For each voltage note the voltmeter, ammeter and wattmeter reading.

Observations:

S. No. Voltage applied Current(amp) Wattmeter reading

Multiplying factor

No load power

V I W M. F. P

Note: a) The no load current of a transformer is generally 2 to 5% of the full load current and is at

a low power factor.b) The multiplying factor of a wattmeter is given by- Voltage rating X current rating X p.f. rating

M. F. = ---------------------------------------------------------- Full scale reading of the transformer

Reports:a) Draw the no load circuit diagram for single phase transformer.b) Calculate and tabulate the no load parameters for each of the observations, show the

sample calculation.c) Draw the open circuit characteristic. It the magnetization characteristic of the core.d) Can you explain why the no load parameters vary with applied voltage?e) Why is the O.C. test performed with the high voltage side open?

QUES: Which losses are measure in the open circuit test? QUES: In open circuit test what parameters are calculated?QUES: Why the transformer rating is in KVA?

EXPERIMENT NO. 7

Name: Short circuit test on a single phase transformer.

Objective: To determine the copper loss the leakage reactance of a single phase transformer.

Circuit diagram:

Specifications of equipment:

S. No. Item Range Manufacturer Maker’s no.

Procedure:

a) This test is done on high voltage side keeping low voltage side short side shorted. Connect as shown in fig.

b) Note the nameplate rating of the transformer and find the full load current. This test has to be carried for currents ranging upto the full load current. Choose meter ratings accordingly.

c) Apply a very small voltage to the high voltage side so that the ammeter reads 20% of the full load current. Note down ammeter, voltmeter and wattmeter readings. Increase the

voltage slowly so as to obtain observations for current in step of 20% upto the rated current.

Observations:

S. No. Voltmeter reading Ammeter reading

Wattmeter reading(w)

Power in watts

Reports:

a) Calculate and tabulate the values of winding resistance and leakage reactance based on high voltage and low voltage side for each observation. Show only one sample calculation.

b) Calculate copper loss of the transformer at 25%, 50%, 75%, 100% of the load and hence find the efficiency. Ignore no load losses.

QUES: Why the transformer rating is in KVA?QUES: Which losses are measured in the short circuit test?QUES: The wattmeter reading in case of short circuit test is taken to indicate the copper loss. Are there no iron losses occurring under the condition of short circuit test?

EXPERIMENT NO. 8

NAME: Verification of Norton’s Theorem.

THEORY: Any two terminal network composed of a linear passive and active circuit elements may be replaced by an equivalent current source and a parallel resistance. The current of the source is the current measured in the short circuit placed across the terminal pair. The parallel resistance is the equivalent resistance looking into the terminal – pair with all independent power sources within the terminal pair inactive.

Fig.1 (a) shows a network with its terminals A & B. Norton’s equivalent of this network is shown in fig.1 (b). I is the current that would flow if a short circuit placed across A B & Ro is the resistance measured looking into the network at the terminals A B with power sources made inactive.

Network shown in fig .1(b) is an exact equivalent of the network shown in the fig .1(a). current in the resistance RL when connected across the terminals A B is obtained from the Norton’s equivalent circuit as follows. Ro IL = ---------------------- Ro+ RL

Circuit diagram: For experimental verification of the Norton’s theorem consider a typical circuit diagram given in fig .2.

Apparatus required: S.NO. ITEM RATING 1 VOLTMETER V1 0 – 250V 2 V2 0 – 30 -60 – 150 3 RHEOSTAT R1 1.8A - 2.8A 4 R2 “ 5 R3 “ 6 RL “ 7 RP “ 8 AMMETER A 0 – 2 A

Observations & calculations:

(1) From circuit fig .2(a) V1= RL= VL =

(2) From fig.2(b) V1 = should be same as in (1) Short circuit current =

(3) Observations from the circuit shown in fig .2(c) Voltmeter reading ammeter reading Ro= V3/I3 V3 I3 1.2.3.

Average value of Ro = Load resistance RL =

Precautions:1. The circuit should be make correctly.2. The voltmeter and ammeter should be of proper rating.

QUES: Write the Norton’s theorem.QUES: In which circuits the Norton’s theorem can be apply?