25072 Demonstrate knowledge of electromagnetism theory by jal11416

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Demonstrate knowledge of electromagnetism theory

Level                              2

Credits                            5

Purpose       This unit standard covers knowledge of electromagnetism theory which
              underpins all technical careers in the electrical and electronic industries.

              People credited with this unit standard are able to demonstrate knowledge of:
              – magnets and magnetism;
              – a.c. generation;
              – d.c. generation; and
              – the simple d.c. motor.


Subfield                           Electrical Engineering

Domain                             Core Electrical

Status                             Registered

Status date                        22 August 2008

Date version published             22 August 2008

Planned review date                31 December 2010

Entry information                  Open.

Replacement information            This unit standard, unit standard 25070, and unit
                                   standard 25071 replaced unit standard 15843.

Accreditation                      Evaluation of documentation by NZQA and industry.

Standard setting body (SSB)        ElectroTechnology Industry Training Organisation

Accreditation and Moderation Action Plan (AMAP) reference                     0003
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.

Special notes

1   This unit standard has been designed for learning and assessment off-job.




                                                                  New Zealand Qualifications Authority 2010
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2     This unit standard is one of three designed to cover knowledge of magnetism and
      electricity, the others being Unit 25070, Explain the properties of conductors,
      insulators, and semiconductors and their effect on electrical circuits and Unit 25071,
      Demonstrate knowledge of electromotive force (e.m.f.) production. It is
      recommended that competency in unit standards 25070 and 25071 be achieved
      before assessment against this unit standard is attempted.

3     Definitions
      a.c. – alternating current.
      d.c. – direct current.
      e.m.f. – electromotive force.
      r.m.s. – root-mean-square.

4     For assessment purposes:
      a Candidates shall be supplied with formulae involving more than three quantities.
      b Use of a calculator during assessment is permitted.
      c Candidates are expected to express calculated values in the relevant Systeme
        Internationale (SI) units, including multiples and sub-multiples (pico (p) 10-12 ;
        nano (n) 10-9; micro (μ) 10-6; milli (m) 10-3; kilo(k) 103; mega (M) 106; etc) and to
        be able to convert between them.

5     Formulae quoted in this unit standard use internationally recognised symbols and
      units.

6     Conventional current flow direction (positive to negative) is implied. Trainees should
      be aware of the opposite direction of electron flow.

Elements and performance criteria
Element 1

Demonstrate knowledge of magnets and magnetism.

Performance criteria

1.1        Magnetic terms are explained in relation to permanent magnets, in accordance
           with industry practice.

           Range         permanent magnet, magnetic field strength, lines of force,
                         magnetic poles, magnetic flux, flux density.

1.2        The direction of the magnetic field surrounding a current carrying wire is
           determined using any popular rule.

           Range         any popular rule may include but is not limited to – the right-hand
                         screw rule.

1.3        The construction of an electromagnet is described with the aid of a sketch
           indicating current direction and magnet polarity.




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1.4       The transformer principle is explained in terms of induced e.m.f. resulting from
          changing flux linkages.

1.5       Devices using electromagnetic and magnetic properties are described in simple
          terms.

          Range        any two of – loudspeaker, relay, electric bell, moving coil
                       instrument, lifting magnet, electric door lock.

1.6       The purpose and application of magnetic screening is stated in terms of
          protection of sensitive meters and circuitry from magnetic interference.

Element 2

Demonstrate knowledge of a.c. generation.

Performance criteria

2.1       The operation of a simple single-loop, two-pole alternator with slip-rings and
          brushes is described with the aid of a sketch.

2.2       Alternator output for each quarter-cycle through one revolution is described with
          the aid of a sketch, and shows a completed resultant waveform.

2.3       A.c. terms are defined in accordance with industry practice.

          Range        cycle, period, frequency, peak, average, instantaneous, r.m.s.

2.4       The reason for using the r.m.s. value of an a.c. wave form is stated in terms of
          the equivalence of r.m.s. and steady d.c. values for resistive heating effect.

2.5       Values are calculated from a.c. voltage and current wave form data.

          Range        peak, average, r.m.s., frequency, period.

Element 3

Demonstrate knowledge of d.c. generation.

Performance criteria

3.1       The induction of an e.m.f. in a conductor being moved in a magnetic field is
          demonstrated using Fleming's right-hand rule.

3.2       The operation of a simple direct current generator is explained with the aid of a
          sketch.

          Range        simple generator – permanent magnet, single loop of wire, two-
                       segment commutator, carbon brush.




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3.3       Generator output for each quarter-cycle through one revolution is described and
          shows a completed resultant waveform.

Element 4

Demonstrate knowledge of the simple d.c. motor.

Performance criteria

4.1       The direction of the force exerted on a current carrying conductor in a magnetic
          field is determined using any popular rule.

          Range         any popular rule may include but is not limited to – Fleming's left-
                        hand rule.

4.2       The operation of a simple motor is explained with the aid of a sketch showing
          direction of current and polarity of the magnet.

          Range         simple motor – permanent magnet, single loop of wire, two-
                        segment commutator, carbon brush.

Please note

Providers must be accredited by NZQA, or an inter-institutional body with delegated
authority for quality assurance, before they can report credits from assessment against
unit standards or deliver courses of study leading to that assessment.

Industry Training Organisations must be accredited by NZQA before they can register
credits from assessment against unit standards.

Accredited providers and Industry Training Organisations assessing against unit standards
must engage with the moderation system that applies to those standards.

Accreditation requirements and an outline of the moderation system that applies to this
standard are outlined in the Accreditation and Moderation Action Plan (AMAP). The
AMAP also includes useful information about special requirements for organisations
wishing to develop education and training programmes, such as minimum qualifications for
tutors and assessors, and special resource requirements.

Comments on this unit standard

Please contact the ElectroTechnology Industry Training Organisation
reviewcomments@etito.co.nz if you wish to suggest changes to the content of this unit
standard.




                                                                New Zealand Qualifications Authority 2010

								
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