EE040 Projects for Exercising Basic 2 Pr Inst

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SRI LANKA INSTITUTE of ADVANCED TECHNOLOGICAL

EDUCATION

Training Unit

Projects for ExercisingBasic 2Practice

No: EE 040

INDUSTRIETECHNIKINDUSTRIETECHNIK

ELECTRICAL and ELECTRONIC

EN INEERINInstructor Manual


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Training Unit

Projects for Exercising - Basic 2

Practical Part

No.: EE 040

Edition: 2008Al l Rights Reserved

Editor: MCE Industrietechnik Linz GmbH & CoEducation and Training Systems, DM-1Lunzerst rasse 64 P.O.Box 36, A 4031 Linz / Aus triaTel. (+ 43 / 732) 6987 3475Fax (+ 43 / 732) 6980 4271Website: www.mcelinz.com


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EE 040

PROJECTS FOR EXERCISING - BASIC 2

CONTENTS Page

Learning objectives 4

PRACTICAL EXERCISE 1

Electrochemistry - Electrolysis 5


Electrochemistry - Secondary cell 7


Electrochemistry - Lead-acid accumulator 10


Voltage sources under no-load and under load 14


Voltage sources connected in series 17


Voltage sources connected in parallel 19


Magnetic field due to a current in a conductor 22


Magnetic field due to a current in a loop of wire 25


Magnetic field due to a current in a coil 27


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Force between conductors carrying currents 29


Force on a current carrying conductor in a magnetic field 32


Forces on a current carrying coil in a magnetic field 34

PRACTICAL TEST 66


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LEARNING OBJECTIVES

The trainee should

demonstrate the use of electrolysis by using the example of the galvanizing

process.

examine the charging and discharging process of a secondary cell.

charge a lead accumulator, observing the necessary safety regulations.

examine the behaviour of voltage sources under no-load and under load.

make the lines of a magnetic field visible in a conductor carrying a current, a

conductor loop, and a coil with the aid of iron fillings and magnetic needles.

examine the forces acting on a conductor carrying a current and on a coil in a

magnetic field.

This practical section is intended to demonstrate and extend the knowledge gained from

the theoretical part. This can be effected by demonstration, as well as by group work.


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Electrochemistry - Electrolysis

1. TASK

The aim is to demonstrate the use of electrolysis using electroplating (with copper) as an

example.

2. EQUIPMENT

- Copper electrode

- Carbon electrode

- Tank containing electrolyte (CuSO4)

- Power supply

- Ammeter

- Test leads

3. CARRY OUT THE EXERCISE

- Immerse one copper electrode and one carbon electrode in the tank with the

electrolyte (copper sulphate solution).

- Connect the electrodes to the Power supply.


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Anode = copper electrode

Cathode = carbon electrode

- Adjust the voltage so that the current density in the plating tank is 20 mA/cm2 of the

surface to be plated.

Result:

After the demonstration has been completed, the carbon electrode which has been coated

with copper is to have the copper removed by reversing the polarity of the voltage.


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Electrochemistry - Secondary cell

1. TASK

The aim is to examine the charging and discharging processes for secondary cell.

2. EQUIPMENT

- Lead electrodes

- Tank with electrolyte

- Power supply

- Zero center ammeter

- Voltmeter

- Incandescent lamp 2 V

- Lamp holder

- Test leads


Charging process:

- Immerse two lead electrodes, thoroughly cleaned of oxide residue, into the tank

containing electrolyte (dilute sulphuric acid).

- Connect the electrodes to the power supply.


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- Adjust the voltage in such a way that approx. 100 mA d.c. is flowing.

- Allow the charging current to flow a few minutes, and observe the lead electrodes

during the process.

Result:


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Discharge process:

- Replace the Power supply by an incandescent lamp.

- Observe the ammeter and the incandescent lamp.

Result:


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Electrochemistry - Lead-acid accumulator

1. TASK

The aim is to charge a lead-acid accumulator, observing the necessary safety regulations.

2. EQUIPMENT

- Lead-acid accumulator 12 V/42 AH

- Ammeter

- Voltmeter

- Charging unit

- Hydrometer

- Battery tester

- Test leads

- Distilled water


- Set up the circuit for Charging a lead accumulator.


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Safety regulations:

- When transporting accumulators, take care that no electrolyte comes in contact with

the skin or clothing (risk of corrosive burns).

- When charging accumulators, always place them on an acid-resistant surface. Any

electrolyte which flows out will cause damage to the surfaces of workbenches andtables.

- When charging, open the vent plugs; a chemical reaction takes place inside the

accumulator, and this generates gases.

- Accordingly, never smoke in the vicinity of batteries emitting gas, or use a naked flame

when close to them - there is a considerable risk of explosion.

- Never charge up a battery in an unventilated, enclosed area. Switch on a fan and

open the windows.


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Hints for maintenance:

- Clean accumulators, which have become very dirty, with tap water.

- Always ensure that the poles are clean. Clean them and apply petroleum jelly

(vaseline).

- The lead plates must be covered by at least 5 mm of electrolyte.

Any lack of electrolyte should be made up by adding distilled water.

- The charging current should amount to approx. 1/10 of the rated capacitance (rated

capacitance 42 Ah = 4.2 A Charging current).

- When charging the accumulator, make sure the polarity is correct.

- Test the accumulator either with the hydrometer (density of the acid), or by testing the

level of the charge with a battery tester (voltmeter with load resistors connected in

parallel).

- Make intermediate measurements, at specific intervals of time, of the level of the

charge. Use a voltmeter, hydrometer, and the battery tester.

- Enter the measured results in the tables.

Density

[g/cm]

Voltage

[v]

Battery tester

Measurement 1

Measurement 2

Measurement 3

Measurement 4

Measurement 5

Measurement 6

Measurement 7

Measurement 8

Measurement 9

Measurement 10


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Density of acid

[g/cm]

Voltage

[V]

Charged cell

Partially charged cell

Normally discharged cell

Fully discharged cell

- Once the lead-acid accumulator has been charged, the charging process can be

terminated.


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Voltage sources under no-load and under load

1. TASK

The aim is to examine the behaviour of a voltage source under no-load and under load.

2. EQUIPMENT

- Switch

- Incandescent lamp

- Lamp holder

- Battery 1.5 V

- Ammeter

- Voltmeter

- Test leads


- Set up the circuit.


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Voltage source under no-load:

- Measure the no-load voltage U0with the switch open.

- Enter the measured results in the table.

Terminal voltage U [V]

No-load voltage U0 [V]

Result:


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Voltage source under load:

- Measure the current Iand the terminal voltage Uwith the switch closed.

- Enter the measured result in the table.

Terminal voltage U [V]

Current I [A]

Result:


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Voltage sources connected in series

1. TASK

The aim is to examine the behaviour of voltage sources connected in series, under no-

load and under load.

2. EQUIPMENT

- Switch

- Incandescent lamps 1.5 V

- Lamp holder

- Batteries 1.5 V

- Ammeter

- Voltmeter

- Test leads


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- Measure the no-load voltages when the switch is open.

- Measure the current and the terminal voltages with the switch closed.


Switch open:

No-load voltage battery 1 U01[V]


Total no-load voltage U0[V]

Switch closed:

Terminal voltage battery 1 U1[V]


Total terminal voltage U[V]

Current I[A]

Result:


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Voltage sources connected in parallel

1. TASK

The aim is to examine the behaviour of voltage sources connected in parallel, under no-

load and under load.

2. EQUIPMENT

- Switch

- lncandescent lamp 1.5 V

- Lamp holder

- Battery 1.5 V

- Ammeter

- Voltmeter

- Test leads


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- Measure the no-load voltage with the switch open.

- Measure the current and the terminal voltage with the switch closed.

- Enter the measured results in the tables.

Switch open:




Switch closed:




Current I[A]


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Result:

..

..


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"Corkscrew or screw rule":

If we imagine a corkscrew or a screw being screwed in the direction of the current, the

direction of rotation corresponds to the direction of the field lines.


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Magnetic field due to a current in a loop of wire

1. TASK

The aim is to plot the magnetic field due to a current in a circular loop of wire.

2. EQUIPMENT

- Battery 12 V

- Switch, 25

- A Copper conductor, 6 mm

- Consuming component 0.48 / 300 W (ballast resistor)

- Connecting leads, 4 mm

- Paper

- Magnetic needles

- Iron filings



- In order for a current of 25 A to flow, we require a component (ballast resistor) with

0.48 / 300 W.


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The conductor is shaped to form a circular loop and is pushed through the sheet of paper.

Pour some iron filings onto the paper.

- If the switch is now closed, current can flow, and the iron filings will arrange

themselves in a pattern around the conductor.

Result:

- Now repeat the experiment and instead of the iron filings, place three or four magnetic

needles around both conductors.

- Observe the magnetic needles, before and during the current flow.

Result:


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Magnetic field due to a current in a coil

1. TASK

The aim is to show the direction of the magnetic field due to a current in a coil, with the aid

of magnetic needles.

2. EQUIPMENT

- Coil, 10 turns, on a plexiglas plate

- Ammeter

- Magnetic needles

- Power supply

- Test Ieads


- Set up the circuit


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- Place magnetic needles around and inside the coil.

- Now switch an the current supply (max. 7 A direct current).

- Observe the magnetic needles before and during the current flow.

Result:

- The north and south poles of a coil under current can also be determined by the "coil

rule".

Result:


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Force between two conductors carrying currents

1. TASK

The aim is to examine the force between two parallel current carrying conductors.

2. EQUIPMENT

- Metal strip with plugs

- Ammeter

- Power supply

- Test leads

- Switch

- Stand material



Current is allowed to flow in the same direction through the two parallel metal strips.


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- The current supply is now connected (max. 7 A d.c.)

- Observe the metal strips before and after the current flow.

Result:


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- Repeat the test.

The current now flows through the two parallel metal strips in opposite directions.

- Observe the metal strips before and during the current flow.

Result:


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- The power supply is now switched on. The current flows through the conductive

trapeze (approx. 1.5 to 2 A).

- Observe the trapeze.

- Reverse the current flowing in the trapeze (the current flows in the opposite direction).

- Switch the power supply on again, and observe what happens to the trapeze.

- Finally, the permanent magnet is turned round, thus reversing the direction of the

magnetic field. The direction of the current in the conductive trapeze is maintained.


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Result:

- The direction of movement of the conductor can also be determined by means of the

"left-hand-rule".

Result:


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- The power supply is now switched on. The d.c. voltage is slowly increased. The

current (max. 7 A) flows through the coil.

- Observe the coil.

- Now reverse the current flow through the coil.

- Switch the power supply on again, and observe what happens to the coil.

- Finally, the direction of the magnetic field of the permanent magnet is reversed.

Result:


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INSTRUCTIONS for practical exercise

No. 3 Electrochemistry - Lead-acid accumulator


- Set up the circuit for charging a lead-acid accumulator.

Safety regulations:

- When transporting accumulators, take care that no electrolyte comes in contact with

the skin or clothing (risk of corrosive burns).

- When charging accumulators, always place them on an acid-resistant surface. Any

electrolyte which flows out will cause damage to the surfaces of workbenches and

tables.


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Result:

If the voltage source is not under load, the terminal voltage Uis the same as the no-load

voltage U0.

Voltage source under load:

- Measure the current Iand the terminal voltage Uwith the switch closed.

- Enter the measured result in the table.

Terminal voltage U [Y]

Current I[A]

Result:

- Every voltage source under load undergoes an internal voltage drop Ui

- The terminal voltage U, because of this internal voltage drop Ui, is smaller than the no-

load voltage U0.

- Every voltage source has an internal resistance Ri.


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Switch closed:

Terminal voltage battery 1 U01[V]...


Total terminal voltage U0 [V]

Current I [A]

Result:

- The total no-load voltage is as great as the total of the partial no-load voltages.

- The total internal resistance is as great as the total of the partial resistances.

- The capacitance of batteries connected in series is equal to the capacitance of an

individual battery.


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INSTRUCTIONS for practical exercise No. 7

Magnetic field due a current in a conductor



In order for a current of 25 A to flow, we require a consuming component (ballast

resistor) with 0.48 /300 W.

- Pour some iron filings onto the sheet of paper.

- If the switch is now closed, current can flow, and the iron filings will arrange

themselves in a pattern around the conductor.

Result:

When current flows through the conductor, a magnetic field is created around it.


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- Now repeat the experiment and instead of the iron filings, place three or four magnetic

needles around both conductors.

- Observe the magnetic needles, before and during the current flow.

Result:

The conductor loop behaves like a short bar magnet, with a north and south pole.


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INSTRUCTIONS for practical exercise No. 10

Force between conductors carrying currents



Current is allowed to flow in the same direction through the two parallel metal strips.

- The current supply is now connected (max. 7 A d.c.)

- Observe the metal strips before and after the current flow.


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Result:

Two conductors, with current flowing in the same direction through them, attract one

another.

- Repeat the test.

The current now flows through the two parallel metal strips in opposite directions.

- Observe the metal strips before and during the current flow.

Result:

Two conductors which have current flowing through them in opposite directions repel one

another.


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- The power supply is now switched on. The d.c. voltage is slowly increased. The

current I(max. 7 A) flows through the coil.

- Observe the coil.

- Now reverse the current flow through the coil (the current flow is inverted).

- Switch the power supply on again, and observe what happens to the coil.

- Finally, the direction of the magnetic field of the permanent magnet is reversed.

Result:

- A coil carrying a current rotates in a magnetic field.

- The direction of rotation of the coil is dependent on the direction of the current I

through the coil, and on the direction of the magnetic field.


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Evaluation Sheet for Practical Exercises


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KEY TO EVALUATION

PER CENT MARK

88 100 1

75 87 2

62 74 3

50 61 4

0 49 5


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Practical Test


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PRACTICAL TEST

Connecting voltage sources.

1. TASK

Connect 4.5 V voltage sources in such a way that a 12 V incandescent lamp can be

operated.

- Design the circuit.

- Measure the current I, the no-load voltage U0, and the terminal voltage U.


2. EQUIPMENT

- Switch, single-pole

- Incandescent lamp 12 V

- Lamp holder

- Batteries 4.5 V

- Ammeter

- Voltmeter

- Test leads


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Circuit diagram:

Switch open:


Switched closed:


Current I [A]


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Documents

EE040 Projects for Exercising Basic 2 Pr Inst