1

UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATION

REVITALISATION PROJECT-PHASE II

+_

I

Low High

+_

V

Low High

10 Ohms10 Ohms

100 voltsR

YEAR I- SEMESTER I

PRACTICAL

Version 1: December 2008

NATIONAL DIPLOMA IN

ELECTRICAL ENGINEERING TECHNOLOGY

ELECTRICAL ENGINEERING

SCIENCE (I)

COURSE CODE: EEC 115

TABLE OF CONTENTS

WEEK 1: Basic Electrical quantities measurement

WEEK 2: Measurement of voltage and current

WEEK 3: Measurement of resistance

WEEK 4: Ohm’s law

WEEK 5: Series circuit connections

WEEK 6: Parallel circuit connections

WEEK 7: Resistance in parallel

WEEK 8: Capacitor in circuit

WEEK 9: Voltage division principle

WEEK 10: Series-parallel connected resistors

WEEK 11: Kirchhoff’s current law

WEEK 12: Kirchhoff’s voltage law

WEEK 13: Resistivity

WEEK 14: Power in d.c. circuit

WEEK 15: Charging and discharging of a capacitor

Basic Electrical Quantities Measurement Week 1

1

TITLE:- Basic Electrical Quantities Measurement

It is necessary knowing how to measure voltage, current, and resistance. Special

types of instruments are used to measure these basic electrical quantities. The instrument

used to measure voltages is a voltmeter, the instrument used to measure current is a

ammeter, and the instrument used to measure resistance is a ohmmeter.

Commonly, all three instruments are combined into a single instrument such as a

multimeter or AVO meter ( Ampere- Volt-Ohmmeter), in which you can choose what

specific quantity to measure by selecting the switch setting.

Figure (1) shows typical portable multimeters, part (a) from figure shows analog

multimeter with pointer, and part (b) shows a digital multimeter with digital screen.

(a) Analog multimeter (b) Digital multimeter Figure (1) Typical portable Multimeter

General scheme symbols is used to indicate placement of meters in circuit when value

changes need to be shown. Figure (2) shows meter symbols used to present the different

meters, as voltmeter, ammeter and ohmmeter.

Basic Electrical Quantities Measurement Week 1

2

A

+ _

Ω

+ _

V

+ _

0.00

+ _A

0.00

+ _V

0.00

+ _Ω

(c) Ohmmeter

(b) Ammeter

(a) Voltmeter

Figure (2) Meter symbols

How to use Analogue meter:

Figure (3) shows a typical multimeter. This device can measures the three electric

quantities. The following step shows how to obtain readings from a multimeter.

1.Set the range of the desired quantity to be measured to the highest value.

2.Connect the leads to the right terminals at the meter

3.Switch on the circuit if necessary.

4.Adjust the range until you get clear readings.

5.Apply the following formula to obtain the measured quantity.

ScaleFull

Rangeading

Re

For example, referring to figure (3),the reading was 3.5 from a full-scale value of 5V, as

shown in the small box.The range was set to X300V.So the measured voltage is

Basic Electrical Quantities Measurement Week 1

3

2105

3005.3

600

300

60

12

3

0.06

1.2

12

120

x1

x10

x1k

X100k

x100

600

300

60

12

0.3

AC VOLT

OHMS

DC VOLT

DC Current

1

2

3

4

5

10

20

50

0

Ω

Scale

Range

Pointer Reading =3.5

Off

0

50

100200

500

1k

5k

20k

30

40

6 8 1012

14

15

0

2

40 VAC

ADC

VDC

3

4

ΩA VCommon

Figure(3): Multimeter

Note:

The scale has to be viewed from an angle perpendicular to it.

Measurement of Voltage and Current Week 2

4

TITLE: Measuring the Voltage

Voltage can be considered as the pressure that force the electrons to flow. The voltage

is being measured by measuring the difference between the voltages at the two terminals of

the device-under-test which is the (voltage drop). This can be performed using a measuring

instrument called voltmeter.

The voltmeter connection in the circuit is a parallel connection.

Figure (1) illustrates how to connect voltmeter in the circuit to measure the voltage

across the resistor.

I R

+ _

I R

+ _V

+

_

V

0.00

+ _V

Figure (1) Example of a voltmeter connection

Procedure

1. Adjust the range of the meter

2. Connect the leads in the true terminals of the meter

3. Apply the other ends of the leads to the resistor under test

4. Record the reading and apply the formula scalefull

Rangeading

Re

Measurement of Voltage and Current Week 2

5

Measuring Current with Ammeter

It is well known that current in the circuit is measured by ammeter, to measure the

current , the circuit must be open and the ammeter is connected in series the circuit.

Procedure

1. Connect the simple circuit shown in the figure below

2. Open the circuit between the source and the resistor

3. Connect the ammeter terminals to one end of the resistor and to the source

4. Switch on the power supply and record the reading.

5. Apply the formula scalefull

Rangeading

Re if necessary

Note:

If the meter did not give any movement or tried to move backward, then switch the terminal

leads with each other

Measurement of Voltage and Current Week 2

6

Figure(1) illustrates how to connect ammeter in the circuit and measure the current.

0.00

+ _A

I

A+ _

R

+ _R

+ _

R

+ _

I

I R

+ _V

R

+ _V

R

+ _V

I

(a) Circuit in which the current is to be measured.

(b) Open the circuit between the resistor and the positive terminal

of battery.

(c) Install the ammeter in the current pass with polarity as shown

(negative to negative, positive to positive)

Figure 1: Example of an ammeter connection

Measurement of Resistance Week 3

7

TITLE:- Measuring Resistance with Ohmmeter

To measure resistance, connect the ohmmeter across the resistor. The resistor must first

remove from the circuit. This procedure is shown in figure (2).

R

+ _

R

+ _V

+

_

Ω

0.00

+ _Ω

Figure (2) Example of using ohmmeter

Procedure

1. Adjust the meter so that when the two terminals are short circuited, the ohmmeter reads

zero

2. Disconnect the resistor to be measured from the circuit (why?)

3. Apply the meter leads to the resistor terminals (resistor is parallel to the meter)

4. Record the reading and apply the formula scalefull

Rangeading

Re if necessary

Ohm’s Law Week 4

8

TITLE: Ohm's law

OBJECTIVE:- Verification of Ohm’s Law

Ohm’s law is the most important mathematical relationship between voltage, current

and resistance in electricity.

It is important to know how to read the resistors' colour code and hence its ohmic value. In

the following figure it shows a table of the meaning of each colour. For example, for the

resistor in the figure(1),the value of the resistor is 200kΩ,since the band 1 is red i.e.

equivalent to 2 in the table ,band 2 is black equivalent to zero in the table and the band 3 is

yellow indicating of a multiplier of 10,000.see at the bottom of the figure.

The fourth band is the tolerance band i.e the percentage of error. It usually comes in

two colors ,the silver indicates ±5% and the gold indicates ±10%.so for example, the value

resistor will lie between 210kΩ and 190kΩ.

Procedure

1. Select a number of different resistors

2. Use the table below to determine their values

3. Use ohmmeter to measure the same resistors you figured out

4. Compare your calculated values with the readings you obtained

V = I X R

Ohm’s Law Week 4

9

Resistors color code:

Band 1:Figure 1Band2:Figure 2

Multiplier Tolerance

Black

Brown

Red

Orange

Yellow

Green

Blue

Violet

Grey

White

First figure

value

0

1

2

3

4

5

6

7

8

9

X1

X10

X100

X1000

X10,000

X100,000

X1,000,000

X10,000,000

X100,000,000

X1,000,000,000

Second

figure value

0

1

2

3

4

5

6

7

8

9

Colour Multiplier

2 0 X10,000=200K %5

Figure 1:Resistors colour code

Series Circuit Connection Week

10

TITLE:- series circuit

OBJECTIVE: verification of series circuit

There are three basic types of circuits, series, parallel and series-parallel circuits.

Series circuit:

Series circuit is the simplest circuit. The conductors, loads and power supply are connected with

only one path for the current. The same amount of current will flow through each load. However,

the voltage across each load will be different. Figure(1) shows different configuration of series

circuits.

Procedure:

1. Connect a number of resistors is series

2. Measure the current in the circuit. What do you notice?

3. Connect two identical lamps in series. Notice the brightness of the lamps

4. Add one more lamp to the circuit you connected in step 3. What do you notice?

5. Repeat step 4 with more lamps and measure the current in all cases

6. Write a conclusion

Series Circuit Connection Week

11

The Electric Current

A B

A B

Figure1 : Different configuration of series circuits

Parallel Circuit Connections Week 6

12

TITLE: Parallel circuit:

OBJECTIVE: To verify parallel circuit

The main difference between a series circuit and a parallel circuit is in the way the

components are connected. Parallel circuit should have at least two loads connected

separately to the voltage source, so the voltage across the loads are the same. However, in a

parallel circuit the electric current has several paths that it can travel. Figure(2) shows

different configuration of parallel circuits.

Procedure

1. Connect a number of resistors is parallel as shown below

2. Measure the current in each branch and the total current. Comment on the

readings

3. Add more resistors in parallel. Repeat step 2

4. Measure the voltage across each resistor. Comment on your results

A

B

BA

Parallel Circuit Connections Week 6

13

A

B

+

_

A

B

+

_

IT

IT

I1

I2 I1 I2

IT

IT

A

B

+

_

IT

IT

I1

I2

Figure1: Differe

Resistance in Parallel Week 7

14

TITLE:- Resistance of parallel connected resistors

OBJECTIVE: To verify parallel connection circuits

1. To measure the total resistance of combinations of parallel connected resistors.

A parallel circuit is a circuit with more than one path for current flow. Removing one

branch of a parallel circuit does not affect the operation of (the current in) the remaining

branch circuit. The total resistance of parallel connected resistors is less than the

resistance of smallest branch resistor. There are many parallel circuits in electronic

equipment. The formula for calculating RT for parallel resistors is:

1/RT = 1/R1 + 1/R2 + 1/R3 +……..+ 1/Rn

RT = R1xR2xR3 / R1R2+R2R3+R3R1

Materials Required:

Multi-meter.

Resistors: all ½ watt, 330 Ω, 470 Ω, and two 1200 Ω.

Procedure:

1) Refer to the following figure choose the resistors shown as combination A.

Resistance in Parallel Week 7

15

2) Measure the resistance of each of the resistors supplied for combination A. Record

the measured value of each resistor in the column beneath is colour coded value in the

following table.

3) Measure the RT of the parallel combination and record your reading in the column

label “Measured RT “in the following table.

Parallel

Combination

Colour

coded

value

R1

330 Ω

R1

470 Ω

R1

1200 Ω

R1

1200 Ω

Measured

RT

Ω

Group A Measured

value, Ω X X

Group B Measured

value, Ω X

Group C Measured

value, Ω X X

Questions:

Q1) was the value RT greater or smaller than the value of the smallest branch resistor in each

combination?

Q2) Combination (group C) placed two resistors of equal value in parallel. From the results

of measuring RT of this combination of resistors, suggest a general rule for RT of any two

resistors of equal value connected in parallel.

Ohmmeter

Resistance in Parallel Week 7

16

Q3) what is the RT of three 330 Ω resistors in parallel?

Variable Resistors.

Objective:

To measure resistance between the variable (centre terminal) and the terminals on

other side of it as the shaft of a potentiometer is turned from its minimum to maximum

position.

Materials Required:

1) Multi-meter.

2) Variable Resistor 10000 Ω Potentiometer.

Procedure:

1. Examine the potentiometer assigned to you. Place it so that the shaft points toward

you. Measure and record in the following table the value of potentiometer between

the two outside terminals.

2. Turn the shaft to any position (1) and measure the resistance between the left terminal

(A) and the centre terminal (C) Record this reading in the following table .

3. Without moving the shaft, measure the resistance between the right terminal (B) and

the centre terminal (C), Record this reading RBC in the table.

4. Complete the table.

Resistance in Parallel Week 7

17

Table 6.1

Step Potentiometer

shaft setting

RAB

Ω

RAC

Ω

RBC

Ω RAC + RBC

1 Any X X X

2 Position 1 X

3 Position 2 X

4 C.W X

5 C.C.W X

Questions:

Q1) In the potentiometer above, what is the relation between RAC, RBC, and RAB? Do your

measurements confirm this relation?.

Q2) In what position of the shaft is the resistance between A and B minimum?.

Q3) In what position of the shaft is the resistance between.

A

B

C

Capacitor Week 8

18

TITLE: Capacitor in a circuit

OBJECTIVE: To test capacitor by observing their charging and discharging using an ohmmeter.

Capacitor is a device that stores energy in the electric field created between a pair of conductors

on which equal but opposite electric charges have been placed. Capacitance is a measure of a

capacitor's ability to store charge. A large capacitance means that more charge can be stored.

Capacitance is measured in farads, symbol (F). However 1F is very large, so prefixes are used to

show the smaller values.

Three prefixes (multipliers) are used, µ (micro), n (nano) and p (pico):

µ means 10-6

(millionth), so 1000000µF = 1F

n means 10-9

(thousand-millionth), so 1000nF = 1µF

p means 10-12

(million-millionth), so 1000pF = 1nF

Materials Required: Ohmmeter.

Capacitor.

Fig 8.1

Capacitor Week 8

19

Procedure:

1. Connect the circuit as shown above.

2. Read the ohmmeter and record the conditions of the capacitor which are:

a. If the ohmmeter reading move toward zero and then slowly returns to infinity

means the capacitor is in a good condition.

b. If the ohmmeter move towards zero and remain at zero means the capacitor is

short circuited .

c. If the reading doesn’t change and remains at infinity means the capacitor is open

circuited.

3. Replace the capacitor and repeat step 1 and 2.

4. Repeat step 3 until all capacitors are tested.

Table 8.1

Answer the

following

questions:

Q1) What

is the

meaning of

capacitanc

e?

Q2) Draw

the symbol

Capacitor

Reading Remark

C1

C2

C3

Capacitor Week 8

20

of a capacitor?

Q3) State 1 application for capacitors?

Q4) complete the following:

If the ohmmeter reading move toward zero and then slowly returns to infinity means

………………………

the ohmmeter move towards zero and remain at zero means

…………………………

If the reading doesn’t change and remains at infinity means

…………

Voltage Division Principle Week 9

21

TITLE: Voltage divider

OBJECTIVE: Verify the operation of voltage divider

APPARATUS:

(1) 2 Digital multimeters

(2) Variable power supply

(3) Resistor R1 = 330

Resistor R2 = 1K

Resistor R3 = 500 - Trimmer

PROCEDURES:

(1) Connect a digital multimeter as d.c voltage, and another one as milliammeter fig 9.1

(2) Set the switch S1 to OFF

(3) Adjust the voltage to 5V by turning the variable power supply

(4) Read the value of the voltage V0 (no load) between point 3 and earth and write it

down in table 9.1

(5) Calculate the value of the voltage V0 (no load) and write it in table 9.1

(6) turn the trimmer R3 completely clockwise

(7) Set the switch S1 to ON

(8) Read the values of the voltage and of the current and write them in table 9.1

(9) Repeat the previous operation for all the values of R3 shown in table 9.1

(10) Represent in fig 9.2 the characteristic curve voltage-current of the voltage divider

(11) Comment on the results

Voltage Division Principle Week 9

22

Fig 9.1

Table 9.1: Obtained Results V0(no load [V]

Measured

V0(no load) [V]

calculated R3 [] 500 400 300 200 100 0

V0 [V]

I0[mA]

Fig 9.2

ON

com A V

ON

com A VS

1 2 3

R2

R1

R3

Voltmeter Milliammeter

S1

V0(V)

I0(mA)

Series-Parallel Connection of Resistors Week 10

23

TITLE: Series-Parallel Resistors

OBJECTIVES: Observe the behaviour of series-parallel connected resistors

APPARATUS: (1) Digital multimeter

(2) Resistor R1 = 1K 5%

Resistor R2 = 1K 5%

Resistor R3 = 220K 5%

PROCEDURE:

(1) Set the switches S1 and S2 to ON

(2) Connect a multimeter, set as ohmmeter, fig 10.1

(3) Write down in table 10.1 the value read in the ohmmeter

(4) Calculate the value of the resistance R12 and write down the value in table 10.1

(5) Compare the measured value with the calculated one

(6) Move a terminal of the ohmmeter from the jack 2 to the jack 1

(7) Set the switches S1 to ON, and S2 to OFF

(8) Write down in table 10.1 the value read in the ohmmeter

(9) Calculate value of the resistance R13 and write down the value in table 10.1

(10) Compare the measured value with the calculated one

(11) Set the switches S1 and S2 to ON

(12) Write down in table 10.1 the value read in the ohmmeter

(13) Calculate the value of the resistance Re and write down the value in table 10.1

(14) Comment on the measured value with calculated one

Series-Parallel Connection of Resistors Week 10

24

Fig 10.1

Table 10.1: Obtained Results R12 []

Measured

R12 []

calculated

R13 []

Measured

R13 []

Calculated

Re []

Measured

Re []

Calculated

V

ON

com

1 2 R3

R1 R2

S2 S1

Kirchhoff’s Laws Week 11

25

TITLE:- Kirchhoff’s Current |Law

OBJECTIVE: To verify Kirchhoff’s law

APPARATUS:

(1) Variable power supply

(2) Voltmeter

(3) Milliameter

(4) Resistor R1 = 1K 5%

Resistor R2 = 1K 5%

Resistor R3 = 220K 5%

PROCEDURES:-

(1) Connect multimeter, set as a d.c voltmeter, and another one as milliameter, Fig 11.1

(2) Adjust the voltage to 10V by turning the variable power supply

(3) Set the switches S1 to On, S2 and S3 to OFF.

(4) Write down in table 11.1 the values read on the voltmeter and on the

milliammeter.

(5) Set the switches S2 to ON, and S1 and S2 to OFF

(6) Write down in table 11.1 the values read on the voltmeter and on the

Milliammeter

(7) Set the switches S3 to ON, S1 and S2 to OFF

(8) Write down in table 11.1 the values read on the voltmeter and on the milliammeter

(9) Calculate the value of the current in the single resistors and write down the results in

table 11.1

(10) Compare the calculated values with the measured ones.

(11) Verify that the sum of the current that go in the node 2 is equal to the sum of the

current that go out.

(12) Comment on the result in steps (10) and (11)

Kirchhoff’s Laws Week 11

26

Fig 11.1

Fig 11.1

Table 11.1: Obtained Results

VR1

[V]

I1

[mA]

VR2

[V]

I2

[mA]

VR3

[V]

I3

[mA]

I1

[mA]

I2

[mA]

I3

[mA]

I = 0

Measured Value Calculated value

V

ON

com

ON

com

Millammeter Voltmeter

1 2 2 2

S1 S2 S3

R2 R3 R1

A

Kirchhoff’s Laws Week 12

29

TITLE:- Kirchhoff’s Voltage Law

OBJECTIVE:- To verify Kirchhoff’s Voltage law

APPARATUS:

(1) Variable power supply

(2) Voltmeter X 2

(3) Resistor R1 = 100 5%

Resistor R2 = 220 5%

Resistor R3 = 330 5%

PROCEDURE:

(1) Use two Multimeters, set as dc voltmeters and connect them as it is shown in figure

12.1

(2) Set the switches S1, S2 and S3 to ON

(3) Adjust the voltage to 10V by varying the variable power supply

(4) Write down in table 12.1 the values read on the voltmeters

(5) Move the terminal of the voltmeter 2 on the terminals of the resistance RL (Jacks 4

and 5), measure the voltage drop and write down the value in Table 12.1

(6) Move the terminals of the voltmeter 2 on the terminals of the resistance R3 (Jacks 6

and earth), measure the voltage drop and write down the value in table 12.1

(7) Verify that the sum of the voltage drops on the resistors corresponds to the voltage

VS.

(8) Calculate the value of the voltage drops on the resistors and write down the value in

table 12.1.

(9) Comment on the results in steps (7) and (8).

Kirchhoff’s Laws Week 12

30

Fig 12.1

Table 12.1: Obtained Results

Vs (v) VR1 (V) VR2 (V) VR3 (V) VR1 (V) VR2 (V) VR3 (V) V = VR1 + VR2 + VR3

(V)

Measured Measured value Calculated value Measured/Calculated

V

ON

com V

ON

com A A

Voltmeter 1 Voltmeter 2

1 2 3 4 S1 S2 R1

R2 R3

5 6 S3

VS

Resistivity Week 13

18

TITLE:- Resistivity of a material

OBJECTIVE:- To verify resistivity of a material

APPARTUS:- (1) A length of a given resistance wire

(2) Digital multimetre

(3) Metre rule

(4) Micrometer gauge

PROCEDURE:- (1) Measure the length of the given resistance wire

(2) Measure the diameter, d of the material by a micro meter gauge

(3) Compute the cross sectional area using the formula A = d2/4

(4) Set the digital multimetre to a suitable ohmmeter range and connect across the

resistance wire at various lengths as shown in fig 13.1 below

(5) S tart with a length of 10cm, 20cm, etc and tabulate the result in the form shown in

the table below.

(6) Plot a graph of RA (nm2) against L(cm) and find the slope of the graph.

(7) Comment on the results in step 6.

Table 13.1

L(cm) R() d(mm) A(nm2) RA(nm

2)

10

20

30

40

50

60

70

80

90

Resistivity Week 13

19

Fig 13.1

Fig 13.1

0 10 20 30 40 50 60 70 80 90

Resistance wire Multimeter

Probe

Meter

rule

Power in d.c. Circuit Week 14

31

TITLE:- Experimental determination of power in a d.c circuit

OBJECTIVE:- To determine the power in a d.c circuit.

BACKGROUND INFORMATION

The power of a resistor can be determined in a dc circuit under any of the following

conditions:

(1) if the resistance of the resistor is unknown, but the voltage (V) across the resistor and

current (I) through the resistor can be measured.

i.e Power P = IV, watts.

(2) if the resistance (R) if the resistor and the current through it are known to give,

P = I2R (watts).

(3) if the resistance (R) of the resistor and the voltage across it are known to give

P = V2/R (watts)

PROCEDURE:

(1) Connect the circuit shown in fig 14.1 with the voltmeter V across the resistor R and

the ammeter A in series with it.

(2) Use the ammeter to record the current, I (Ampere) through the resistor and the

voltmeter to record the P.d. (volts) across the resistor.

(3) Determine and record the value of R (in ohms) before the commencement of the

experiment.

Fig 14.1

Voltmeter

Ammeter

R

R

A

V

E

Power in d.c. Circuit Week 14

32

RESULT ANALYSIS:-

Calculate the power P, across the resistor using each and all the formulae stated above.

Charging and Discharging of a Capacitor Week 15

32

TITLE:- Charging and discharging current of a capacitor

OBJECTIVE:- To determine charging and discharging of a capacitor

APPARATUS:-

(1) Potentiometer

(2) Ammeter

(3) Power supply

PROCEDURE:

Capacitor charging

Suppose we have an initially uncharged capacitor C (i.e. having zero voltage across it) in

figure 15.1 and we begin to move the wiper of the potentiometer towards the upper end X.

As this happen the potential difference across the capacitor C gradually increase, and

consequently the amount of charge stored by the capacitor also increase according to the

expression,. Q = CV, in order words, as the slider of the potentiometer moves upwards X, so

the upper plate of C becomes more positively charged with respect to point X which is

earthed (i.e. at zero potential).

Fig 15.1

Capacitor discharge current

Let us refer to fig 15.1 and assume that the capacitor C has been fully charged to the

maximum voltage, E volts of the d.c supply. Once again we bear in mind that the slide of the

potentiometer must have point X for the potential difference across the capacitor to be E

volts. (the maximum value). Now, if the slide of the potentiometer is moved downwards

from X towards position Y (i.e. zero potential), then the capacitor begins to discharge current

from the upper plate of the capacitor (previously at a higher potential) through the ammeter

and the potentiometer to the position T. Under this condition, the current flows through the

ammeter in the opposite direction.

Potentiometer

dischargin

g current

(Capacitor

)

C + _

+

_

E X

Y

+ Upper movement.

Of slide

Vc