eec 115 electrical engg science 1 practical

UNESCOVOCATIONAL EDUCATION

REVITALISATION PROJECT

100 volts

YEAR I

Version 1: December 2008

NATIONALELECTRICAL ENGINEERI

ELECTRICAL ENGINEERING SCIENCE (I)

COURSE CODE

UNESCO-NIGERIA TECHNICAL & VOCATIONAL EDUCATION

REVITALISATION PROJECT -PHASE II

+_

I

Low High

+_

V

Low High

10 Ohms10 Ohmsvolts

R

YEAR I - SEMESTER I

PRACTICAL

Version 1: December 2008

NATIONAL DIPLOMA IN

ELECTRICAL ENGINEERI NG TECHNOLOGY


COURSE CODE: EEC 115

NG TECHNOLOGY

ELECTRICAL ENGINEERING

2

TABLE OF CONTENTS

Department Electrical Engineering Technology

Subject ELECTRICAL ENGINEERING SCIENCE (I)

Year 1

Semester 1

Course Code EEC 115

Credit Hours 3

Theoretical 1

Practical 2


PRACTICAL

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

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This Page is Intentionally Left Blank

4

Basic Electrical Quantities Measurement Week 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.

5

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

2105

3005.3 =×

6

Figure(3): Multimeter

Note:

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

7

Measurement of Voltage and Current Week 2

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.

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

8

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

9

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

Figure 1: Example of an ammeter connection

10

Measurement of Resistance Week 3

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).

+

+

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

11

Ohm’s Law Week 4

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

12

Resistors color code:

Ω %5±

Figure 1:Resistors colour code

13

Series Circuit Connection Week 5

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

14

Figure1 : Different configuration of series circuits

15

Parallel Circuit Connections Week 6

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

16

Figure1: Differe

Resistance in Parallel

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 R

parallel resistors is:

1/RT

RT

Materials Required: Multi-meter.

Resistors: all ½ watt, 330 Ω, 470

Procedure:

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

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.

Resistance in Parallel Week 7

Resistance of parallel connected resistors

To verify parallel connection circuits

To measure the total resistance of combinations of parallel connected resistors

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


branch circuit. The total resistance of parallel connected

han the resistance of smallest branch resistor. There are many

parallel circuits in electronic equipment. The formula for calculating R

T = 1/R1 + 1/R2 + 1/R3 +……..+ 1/Rn

T = R1xR2xR3 / R1R2+R2R3+R3R1

Ω, 470 Ω, and two 1200 Ω.

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

Measure the resistance of each of the resistors supplied for combination A.

measured value of each resistor in the column beneath is colour

coded value in the following table.

Week 7

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

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


branch circuit. The total resistance of parallel connected

han the resistance of smallest branch resistor. There are many

parallel circuits in electronic equipment. The formula for calculating RT for

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

Measure the resistance of each of the resistors supplied for combination A.

measured value of each resistor in the column beneath is colour

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.

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

Ohmmeter

19

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.

A

B

C

20

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.

Capacitor Week 8

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

22

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

Ans

wer

the

foll

owi

ng

que

stio

ns:

Q1)

What is the meaning of capacitance?

Q2) Draw the symbol of a capacitor?

Q3) State 1 application for capacitors?

Q4) complete the following:

Capacitor

Reading Remark

C1

C2

C3

23

• 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

…………

24

Voltage Division Principle Week 9

TITLE: Voltage divider

OBJECTIVE : Verify the operation of voltage divider

APPARATUS:

(1) 2 Digital multimeters

(2) Variable power supply

(3) Resistor R1 = 330Ω

Resistor R2 = 1KΩ

Resistor R3 = 500Ω - 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

25

Fig 9.1

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

Measured V0(no load) [V]

calculated R3 [Ω] 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)

26

Series-Parallel Connection of Resistors Week

10

TITLE: Series-Parallel Resistors

OBJECTIVES: Observe the behaviour of series-parallel connected resistors

APPARATUS: (1) Digital multimeter

(2) Resistor R1 = 1KΩ ± 5%

Resistor R2 = 1KΩ ± 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


(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


(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

27

Fig 10.1

Table 10.1: Obtained Results R12 [ΩΩΩΩ]

Measured

R12 [ΩΩΩΩ]

calculated

R13 [ΩΩΩΩ]

Measured

R13 [ΩΩΩΩ]

Calculated

Re [ΩΩΩΩ]

Measured

Re [ΩΩΩΩ]

Calculated

V

ON

com

1 2 R3

R1 R2

S2 S1

28

Kirchhoff’s Laws Week

11

TITLE :- Kirchhoff’s Current |Law

OBJECTIVE : To verify Kirchhoff’s law

APPARATUS:

(1) Variable power supply

(2) Voltmeter

(3) Milliameter

(4) Resistor R1 = 1KΩ ± 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


Milliammeter

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


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)

29

Fig 11.1 Fig 11.1 Table 11.1: Obtained Results

VR1

[V]

I1

[mA]

VR2

[V]

I 2

[mA]

VR3

[V]

I 3

[mA]

I 1

[mA]

I2

[mA]

I 3

[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

eec 115 electrical engg science 1 practical

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