Direct Current Circuits SAMPLE. Learner workbook. Version 1. Training and Education Support Industry Skills Unit Meadowbank. Product Code: 5623

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1 Learner workbook Version 1 Training and Education Support Industry Skills Unit Meadowbank Product Code: 5623

2 Enquiries Enquiries about this and other publications can be made to: Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE Level 3, Building J, See Street, MEADOWBANK NSW 2114 Tel: Fax: TAFE NSW (Training and Education Support, Industry Skills Unit Meadowbank) 2012 Copyright of this material is reserved to TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. Reproduction or transmittal in whole or in part, other than subject to the provisions of the Copyright Act, is prohibited without the written authority of TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. ISBN

3 Table of Contents Introduction... 5 Section 1 Basic Electrical Concepts... 7 Section 2 Basic Electrical Circuits Section 3 Ohm s Law Section 4 Electrical Power Section 5 Effects of an Electric Current Section 6 Revision, Consolidation and Assessment Section 7 E.M.F. Sources, Energy Sources and Conversion Section 8 Resistors Section 9 Factors Affecting Resistance Section 10 Series Circuits Section 11 Parallel Circuits Section 12 Revision, Consolidation and Assessment Section 13 Series-parallel Circuits Section 14 Effects of Meters in a Circuit Section 15 Resistance Measurement Section 16 Capacitors and capacitance Section 17 Capacitors in Series and Parallel Section 18 Revision, Consolidation and Assessment Review Questions Answers Sample theory test 1 Answers Sample theory test 2 Answers Sample theory test 3 Answers Appendices Resource Evaluation Form TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

4 Risk Assessment Terminology Supervision Level: D Direct This means the personal supervision of a learner, at all times, on a direct and constant basis, within visual contact and/or earshot. Constant basis refers to the continuous supervision of tasks being performed for the first time and until skill is demonstrated for the complexity of the task and work environment. G General This means the learner does not require constant attendance of the supervisor but requires personal contact with an experienced worker on a recurrent basis when working. Periodic supervision means being under instruction and direction for tasks being formed with checks and tests being made prior to the commissioning of apparatus/equipment. B Broad This means the learner does not require constant supervision but requires personal contact with an experienced worker on at least a regular/occasional basis when working. Occasional supervision means being under instruction and direction with checks being carried out on completion of multi-tasks. Risk Classes: A high risk Potential death or permanent disablement) B medium risk Potential serious injury/illness and temporary disablement) C low risk Potential minor injury, no lost time) Page 6 of 314 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

5 Section 1 Basic Electrical Concepts Section Purpose In this section you will learn about the generation, transmission and distribution of electrical energy, the properties of matter and the mechanisms of electric current flow. Section Topics Electrotechnology industry Electricity (static and current) Power generation of electricity Transportation of electricity Utilisation of electricity Basic calculations Learning Objectives At the end of this section you should be able to: (a) Describe the electrotechnology industry. (b) Describe the concepts of static and current electricity. (c) Explain how electricity is produced by renewable and non renewable energy sources. (d) Describe how electricity is transported from the source to the load via the transmission and distribution systems. (e) Explain how electricity is utilised by the various loads. (f) Perform basic calculations involving quantity of electricity, velocity and speed with relationship to the generation and transportation of electricity. Technical Information You will find the information to undertake this section in the following references. At least one reference text should be used. Jenneson, J.R. 2010, Electrical Principles for the Electrical Trades, 6th Ed., McGraw Hill, Sydney. Hampson, J. 2011, Electrical Trade Principles - A Practical Approach, 2nd Ed., Pearson Education, Sydney. Phillips, P. 2012, Electrical Principles, 2nd Ed., Cengage Learning, Melbourne. Batty, I. 1996, Electrical Principles 1, Prentice Hall, Sydney. Lowe JF. 1989, Electronics for the Electrical Trades, 4th Ed., McGraw Hill, Sydney. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 7 of 314

6 Learner Exercises A constant current of 1 ampere is maintained in a circuit for 1 hour. Determine the quantity of electricity used in coulombs. Solution: Step 1. Step 2. List data and make sure it is in S.I. units I = 1 A t = 1 h = 3600 s Q = It State equation and substitute data = I x 3600 = 3600 C Step 3. Answer = 3600 C or 3600 coulombs Learner Exercise 1.1 A cell supplies a current of 5 amperes continuously to a circuit for 48 minutes. Determine the quantity of electricity passed through the cell and delivered to the circuit. Learner Exercise 1.2 An electro chemical separation bath requires coulombs of electricity for 1 hour. What is the value of current? (Hint: you will need to transpose the equation to make I the new subject) Learner Exercise 1.3 How many minutes would it take a steady current of 15 amperes to supply 1350 coulombs of electricity to a circuit? (Hint: you will need to transpose the equation to make time subject) the new Page 8 of 314 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

7 Learner Exercise 1.4 A motor cyclist leaves home and travels 50 km East, 40 km North and 20 km West. If the journey takes two hours, calculate: (i) his speed in kmh -1 (ii) his velocity in ms -1 Learner Exercise 1.5 Draw and label a block diagram to outline the components of the electricity generation, transmission and distribution system in Australia. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 9 of 314

8 Review Questions These questions will help you revise what you have learnt in Section The smallest possible part of an element that can exist in free state is. 2. A negative ion is one having of electrons. 3. All electrons have a electrical charge. 4. A is the fundamental positively charged particle of an atom. 5. An atom with a deficiency of is termed a positive ion. 6. The nucleus of an atom consists of neutrons, which have no resultant charge, and which have a charge. 7. The practical S.I. unit of velocity is the. 8. In the atomic structure of an element, a negative charge is exhibited by the: (A) electron (B) neutron (C) proton (D) atom. 9. In the atomic structure of an element, a positive charge is exhibited by the: (A) electron (B) neutron (C) proton (D) isotope. (D) atom. 10. An atom that has gained or lost an electron is termed a/an: (A) atom (B) nucleus (C) ion Page 10 of 314 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

9 11. Conduction of electric current through a gas is achieved by: (A) breaking of covalent bonds (B) the kinetic energy theory of gases (C) dislodging protons from the nucleus of gas atoms (D) ionisation of the gas. 12. In the atomic structure of an element, a zero charge is exhibited by the: (A) (B) (C) (D) electron nucleus proton atom. 13. A positive ion is an atom that has: (A) (B) (C) (D) gained an electron lost an electron gained an electric charge been rendered electrically neutral. 14. A material that requires a relatively small amount of energy to remove the outer electron away from its atoms would be termed: (A) (B) (C) (D) pentavalent material good insulator good conductor poor conductor. 15. Current in a solid conductor is a result of movement in: (A) (B) (C) (D) free electrons the conductor negative ions electron orbits. 16. A solution capable of conducting an electric current is called: (A) an electrolysis (B) an electrolyte (C) a hydroelectric solution (D) a dielectric solution. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 11 of 314

10 17. Electric current is a movement of positive and negative ions in: (A) a copper conductor (B) a carbon conductor (C) a semiconductor (D) an electrolyte. 18. A circuit takes a steady current of 5 amperes for 40 minutes. Determine the quantity of electricity supplied to the circuit. 19. If an electric welding machine takes a current of 60 amperes for 2 minutes, what quantity of electricity would be required? 20. It requires coulombs to fully charge a battery. If the current is maintained at 2 amperes, how long will it take to charge the battery? 21. An electroplating bath has coulombs of electricity supplied to it in 10 minutes. Determine the current in amperes. 22. A car is moving at 40 km/h. What is its velocity in m/s? 23. The velocity of a bullet is 800 m/s. Assuming no losses, how far will the bullet travel in 8 seconds? 24. List five methods of producing electricity and classify each of them as either renewable or non-renewable. Page 12 of 314 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

11 Summary of Technical Information Basic Electrical Concepts The electrotechnology industry covers a large range of industries including electrical installation, maintenance and servicing, electronics, data communications, air conditioning, refrigeration, security and fire protection. Most electricity generated in Australia comes from coal burning thermal power stations and is supplemented by some renewable energy sources such as hydroelectric power stations, wind turbines and photovoltaic sources. The electricity generated in the large power stations is transported through transmission and distribution networks to reach the consumer where it is utilised in electric motors, lighting, heating appliances and so on. Matter may be defined as anything which occupies space. Matter exists in either of three forms: solid, liquid and gas. A substance is a definite kind of matter, all specimens of which have the same physical and chemical properties. An element is a substance which cannot be separated into simpler substances by chemical means. Compound substances are made up by chemical combination of definite proportions of two or more elements. A mixture is composed of two or more substances which do not enter into chemical union, and in which the separate natures of the mixed substances may be determined by other than chemical means. An atom is the smallest part of an element which can enter into a chemical change. A molecule is the smallest particle of a substance which can exist and still have all the properties and characteristics of the substance. In a solid, the molecules firmly adhere together and strongly resist being separated. In a liquid, the molecules are separated and the liquid takes up the shape of the containing vessel. The molecules of a gas are in a constantly turbulent condition, colliding with each other, and striking against the walls of any containing vessel, thus causing their dispersal throughout the available space. Temperature, and to a lesser extent pressure, largely determine the state of a substance. The usual effects of increasing the temperature of a substance are to increase the rate of vibration of the molecules and to expand the substance. The electron theory states that all matter is composed of positive and negative electric charges. An electron is a negatively charged particle of an atom. It can sometimes be separated from its atom and as such is called a free electron. A proton is a positively charged particle of an atom. A proton cannot readily be separated from its atom. The mass of a proton is 1,836 times that of an electron. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 13 of 314