Effects Of Electrical Current

Question 1

List off four physiological effects of current flow on the human body.

Answer 1

1. Burns
2. Muscle contractions and spasms
3. Neurological damage
4. Cardiac arrest
5. Loss of consciousness
6. Ventricular Fibrillation

Question 2

List four factors which affect the severity of an electric shock.

Answer 2

1. Time exposed
2. Current intensity
3. Path travelled through the body
4. Voltage

Question 3

What level of amperage does muscular paralysis usually occur?

Answer 3

10-50mA

Question 4

Define ‘Direct Contact’.

Answer 4

1.4.38
Contact, Direct
Contact with a conductor or conductive part that is live in normal service.

Question 5

Define ‘Indirect Contact’.

Answer 5

1.4.39
Contact, Indirect
Contact with a conductive part that is not normally live but has become live under fault conditions (because of insulation failure or some other cause).

Question 6

Describe two of the fundamental principles listed in AS/NZS3000 for personal protection from direct contact with live parts.

Answer 6

1. Insulation
2. Barriers or enclosures
3. Obstacles
4. Placing out of reach

Question 7

Describe two of the fundamental principles listed in AS/NZS3000 for personal protection from indirect contact.

Answer 7

1. Automatic disconnect of supply
2. Prevent fault current passing through the body by using Class II insulation, or double insulated.
3. Electrical separation
4. Limit the value of shock current.

Question 8

Describe two of the fundamental principles listed in AS/NZS3000 for personal protection from indirect contact.

Answer 8

1. Automatic disconnect of supply
2. Prevent fault current passing through the body by using Class II insulation, or double insulated.
3. Electrical separation
4. Limit the value of shock current.

Question 9

List two tips you could follow to minimise the chances of getting an electric shock.

Answer 9

1. Lock out and tag out the circuit you intend to work on.
2. Test before you touch with a multimeter, testing the multimeter before and after testing the circuit.
3. Remove conductive jewellery or clothing.
4. Never work on live conductors.

Question 10

Apart from electric shock to persons or livestock, what do we, as electricians need to ensure with designing and installing? How is this achieved?

Answer 10

That the electrical components do not cause excessive temperatures or create explosive atmospheres.

Elite workmanship.
Design the circuit in alignment with AS/NZS 3000 guidelines.

Question 11

State four common effects of electric current flow and give one beneficial examples of each.

Answer 11

1. Heating Effect
   • Description: When current flows through a conductor, it produces heat due to resistance.
   • Beneficial Example: Electric heaters convert electrical energy into heat to warm homes.
   
   2. Magnetic Effect
      • Description: Electric current creates a magnetic field around the conductor.
      • Beneficial Example: Electric motors use this principle to convert electrical energy into mechanical motion.
   3. Chemical Effect (Electrolysis)
      • Description: Electric current causes chemical changes, especially in liquids (electrolytes).
      • Beneficial Example: Electroplating uses current to coat objects with a thin layer of metal for corrosion resistance or decoration.
   4. Lighting Effect
      • Description: Electric current can produce light, either by heating a filament or exciting gases.
      • Beneficial Example: Electric bulbs and LED lights illuminate homes, streets, and workplaces.
   5. Physiological Effect
      • Description: Electric current can affect nerve and muscle function in the human body.
      • Beneficial Example: Electrotherapy in medicine is used for pain relief and muscle stimulation during rehabilitation.

Question 12

Apart from physiological, name a negative effect of electric current flow and where would you common see this effect?

Answer 12

A common negative effect of electric current flow is the heating effect, where current flowing through a conductor generates heat.

Another common negative effect is electrolysis, often seen in boiler, hot water systems and marine environments.

Question 13

What conditions are necessary for ‘electrolytic corrosion’ to occur?

Answer 13

1. An Anode and a Cathode:
   An anode is the area where metal is oxidized and loses electrons, essentially the location where corrosion occurs.
   A cathode is the area where electrons are received and a reduction reaction takes place.
   These two areas must be present and in contact with each other for the corrosion process to initiate.
2. An Electrolyte:
   An electrolyte is a conductive solution that allows ions to move between the anode and cathode.
   Examples include water, saltwater, or other conductive liquids.
   The presence of an electrolyte is crucial for ionic current flow, which is necessary for the corrosion process to continue.
3. A Return Path for Electron Flow:
   An electrical pathway must exist to allow electrons to move from the anode to the cathode, completing the electrochemical circuit.
   This can be a physical connection between the anode and cathode, like a metal wire.
4. A Potential Difference:
   A voltage difference (potential difference) between the anode and cathode is also necessary to drive the electrochemical reaction.
   This potential difference is created by the difference in electrochemical properties between the two areas.

Question 14

What is the name of the device used to combat electrolytic corrosion? and;
How does this practice work?

Answer 14

Galvanic/Sacrificial Anode Systems.

These systems use a more reactive metal, like zinc or magnesium, as an anode. This anode connects to the metal structure being protected. The more reactive anode corrodes instead of the protected structure, essentially sacrificing itself to prevent corrosion. This is why they are also called sacrificial anode systems.

Question 15

What are the two effects of an electric current through a conductor, that ALWAYS occurs?

Answer 15

Magnetism
Heat