Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

UNESCO-NIGERIA TECHNICAL &
VOCATIONAL EDUCATION
REVITALISATION PROJECT-PHASE II

NATIONAL DIPLOMA IN
ELECTRICAL ENGINEERING TECHNOLOGY

Low

_

Low

High

I

10 Ohms
10 Ohms

High

_

+

V

+

R

100 volts

ELECTRICAL ENGINEERING
SCIENCE (I)
COURSE CODE: EEC 115
YEAR I- SEMESTER I
PRACTICAL
Version 1: December 2008

1

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
...
circuit
WEEK 15: Charging and discharging of a capacitor

Basic Electrical Quantities Measurement

Week 1

TITLE:- Basic Electrical Quantities Measurement
It is necessary knowing how to measure voltage, current, and resistance
...
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
...

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
...
Figure (2) shows meter symbols used to present the different
meters, as voltmeter, ammeter and ohmmeter
...
00

Week 1

+

Basic Electrical Quantities Measurement

(a) Voltmeter
0
...
00

+ Ω _

(c) Ohmmeter

Figure (2) Meter symbols

How to use Analogue meter:
Figure (3) shows a typical multimeter
...
The following step shows how to obtain readings from a multimeter
...
Set the range of the desired quantity to be measured to the highest value
...
Connect the leads to the right terminals at the meter
3
...

4
...

5
...


Re ading 

Range
Full  Scale

For example, referring to figure (3),the reading was 3
...
The range was set to X300V
...
5 
6

300
 210
5

8

10

12

4

14

2
20

30

200

500

ADC

100

1k

0

50

50

5k
20k

2
1

Scale

15

40

10

0

VDC

Week 1

0

3
4

0

5

Ω

VAC

3
4

Reading =3
...
3

DC VOLT

60
12
3

0
...
2
12
120

x100
x1k
X100k

AC VOLT

Common

A

Ω

OHMS

V

Figure(3): Multimeter

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


The voltmeter connection in the circuit is a parallel connection
...


0
...


Adjust the range of the meter

2
...


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

4
...


Procedure
1
...


Open the circuit between the source and the resistor

3
...


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


Apply the formula Re ading 

Range
if necessary
full  scale

Note:
If the meter did not give any movement or tried to move backward, then switch the terminal
leads with each other

5

Measurement of Voltage and Current

Week 2

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


R

R

+

_

_

+

V

(b) Open the circuit between the resistor and the positive terminal
of battery
...
00

_

R

+

I

+

+

R

V

_

I

A

_

+ A _

(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

6

Measurement of Resistance

Week 3

TITLE:- Measuring Resistance with Ohmmeter
To measure resistance, connect the ohmmeter across the resistor
...
This procedure is shown in figure (2)
...
00

+

+ Ω _

R

R

Ω

V

_

_

+

_
+

Figure (2) Example of using ohmmeter

Procedure
1
...


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

3
...


Record the reading and apply the formula Re ading 

Range
if necessary
full  scale

7

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
...
In
the following figure it shows a table of the meaning of each colour
...
e
...
see at the bottom of the figure
...
e the percentage of error
...
so for example, the value
resistor will lie between 210kΩ and 190kΩ
...


Select a number of different resistors

2
...


Use ohmmeter to measure the same resistors you figured out

4
...


Series circuit:
Series circuit is the simplest circuit
...
The same amount of current will flow through each load
...
Figure(1) shows different configuration of series
circuits
...


Connect a number of resistors is series

2
...
What do you notice?

3
...
Notice the brightness of the lamps

4
...
What do you notice?

5
...


Write a conclusion

10

Series Circuit Connection
A

Week
B

A

B

The Electric Current

Figure1 : Different configuration of series circuits

11

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
...
However, in a
parallel circuit the electric current has several paths that it can travel
...


Procedure
1
...


Measure the current in each branch and the total current
...


Add more resistors in parallel
...


Measure the voltage across each resistor
...
To measure the total resistance of combinations of parallel connected resistors
...
Removing one
branch of a parallel circuit does not affect the operation of (the current in) the remaining
branch circuit
...
There are many parallel circuits in electronic
equipment
...
+ 1/Rn

RT = R1xR2xR3 / R1R2+R2R3+R3R1
Materials Required:
Multi-meter
...


Procedure:
1) Refer to the following figure choose the resistors shown as combination A
...
Record
the measured value of each resistor in the column beneath is colour coded value in the
following table
...


Ohmmeter

Parallel
Combination
Group A
Group B
Group C

Colour
coded
value
Measured
value, Ω
Measured
value, Ω
Measured
value, Ω

R1

R1

R1

R1

330 Ω

470 Ω

1200 Ω

1200 Ω

X

Measured
RT
Ω

X
X

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
...

15

Resistance in Parallel

Week 7

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

Variable Resistors
...


Materials Required:
1) Multi-meter
...


Procedure:
1
...
Place it so that the shaft points toward
you
...

2
...

3
...

4
...


16

Resistance in Parallel

Week 7
A

C
B

Table 6
...
W

X

5

C
...
W

RAC
Ω

RBC
Ω

RAC + RBC

X

X

X

X

Questions:
Q1) In the potentiometer above, what is the relation between RAC, RBC, and RAB? Do your
measurements confirm this relation?
...

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


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
...
A large capacitance means that more charge can be stored
...
However 1F is very large, so prefixes are used to
show the smaller values
...

Capacitor
...
1

18

Capacitor

Week 8

Procedure:
1
...


2
...
If the ohmmeter reading move toward zero and then slowly returns to infinity
means the capacitor is in a good condition
...
If the ohmmeter move towards zero and remain at zero means the capacitor is
short circuited
...
If the reading doesn’t change and remains at infinity means the capacitor is open
circuited
...
Replace the capacitor and repeat step 1 and 2
...
Repeat step 3 until all capacitors are tested
...
1

Capacitor

Reading

Remark

Answer the
following

C1

questions:

Q1) What

C2

is the
meaning of
capacitanc

C3

e?
Q2) Draw
the symbol
19

Capacitor

Week 8

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
…………

20

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 = 330
Resistor R2 = 1K
Resistor R3 = 500 - Trimmer

PROCEDURES:
(1)

Connect a digital multimeter as d
...
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

(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

(10)

Represent in fig 9
...
1

Table 9
...
2
22

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 = 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 the value read in the ohmmeter

(4)

Calculate the value of the resistance R12 and write down the value 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 the value read in the ohmmeter

(13)

Calculate the value of the resistance Re and write down the value in table 10
...
1

Table 10
...
c voltmeter, and another one as milliameter, Fig 11
...


(4)

Write down in table 11
...


(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

(9)

Calculate the value of the current in the single resistors and write down the results in
table 11
...


(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
...
1
R1
com

R3

R2

com

A

V

Fig 11
...
1: Obtained Results
VR1

I1

VR2

I2

VR3

I3

I1

I2

I3

[V]

[mA]

[V]

[mA]

[V]

[mA]

[mA]

[mA]

I=0

[mA]

Measured Value

Calculated value

26

Kirchhoff’s Laws

Week 12

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 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

(7)

Verify that the sum of the voltage drops on the resistors corresponds to the voltage
VS
...
1
...


29

Kirchhoff’s Laws

1

R1

2

3

S2

4

VS

ON

A

S1

Week 12

com

ON

A

V

6
Voltmeter 1

com

V

5

S3

R2

R3

Voltmeter 2

Fig 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

30

Resistivity

Week 13

TITLE:- Resistivity of a material
OBJECTIVE:- To verify resistivity of a material
APPARTUS:(1)
(2)
(3)
(4)

A length of a given resistance wire
Digital multimetre
Metre rule
Micrometer gauge

PROCEDURE:(1)
(2)
(3)
(4)
(5)

(6)
(7)

Measure the length of the given resistance wire
Measure the diameter, d of the material by a micro meter gauge
Compute the cross sectional area using the formula A = d2/4
Set the digital multimetre to a suitable ohmmeter range and connect across the
resistance wire at various lengths as shown in fig 13
...


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


Table 13
...
1
Probe

Fig 13
...
c
...
c circuit
OBJECTIVE:- To determine the power in a d
...

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
...
e Power P = IV, watts
...

(3)
if the resistance (R) of the resistor and the voltage across it are known to give
P = V2/R (watts)

PROCEDURE:
(1)
(2)
(3)

Connect the circuit shown in fig 14
...

Use the ammeter to record the current, I (Ampere) through the resistor and the
voltmeter to record the P
...
(volts) across the resistor
...

Voltmeter

V
R

E

A

Ammeter

R

Fig 14
...
c
...


32

Charging and Discharging of a Capacitor

Week 15

TITLE:- Charging and discharging current of a capacitor
OBJECTIVE:- To determine charging and discharging of a capacitor
APPARATUS:(1)
(2)
(3)

Potentiometer
Ammeter
Power supply

PROCEDURE:
Capacitor charging
Suppose we have an initially uncharged capacitor C (i
...
having zero voltage across it) in
figure 15
...

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,
...
e
...

+
+ Upper movement
...
1

Capacitor discharge current
Let us refer to fig 15
...
c supply
...
(the maximum value)
...
e
...
Under this condition, the current flows through the
ammeter in the opposite direction

---