Element 5 Flashcards
Identify the basic parameters of an electrical system?
- Voltage.
- Current.
- Resistance.
What is the relationship called, that links Voltage, Current and Resistance?
- Ohm’s Law
List the hazards of electricity?
- Electric shock.
- Burns (direct and indirect).
- Fire and explosion.
- Arcing and secondary effects.
Identify some effects when somebody receives an electric shock?
- Mild discomfort.
- Muscle tremor.
- Uncontrollable muscle contractions.
- Respiratory failure.
- Ventricular fibrillation.
- Cardiac arrest.
- Severe burns.
Outline the factors that will influence the severity of any injury sustained from electricity?
- System voltage.
- Duration of contact.
- Pathway through the body.
- Body resistance.
- Contact surface area.
- Environmental factors.
- Frequency.
List the reasons why portable electrical equipment is often involved in electrical accidents?
- Frequently unsuitable for the job being done.
- Misuse.
- Not inspected.
- Not maintained.
Outline some high-risk work activities involving electricity?
- Using poorly maintained electrical equipment.
- Working near overhead power lines.
- Contact with underground power cables.
- Working on live supplies.
- Using electrical equipment in wet environments.
Draw a simple equation to illustrate Ohm’s Law?
Voltage = Current x Resistance Volts = Amps x Ohms V = I x R
Identify the 2 types of current ?
- Direct Current (DC).
- Alternating Current (AC).
What is the mains electricity supply in the UK?
- 230 volts (50 hertz).
Explain the meaning of “Live” and “Dead”?
- When a system is connected to an electrical power source it is described as “Live” (in some countries it is described as “Hot”).
Once it has been disconnected from its power source it might be described as “Dead”.
Define “Direct” electrical burns?
Where a CURRENT causes overheating as it passes through the skin and internal tissues of the body.
Define “Indirect” electrical burns?
Does not occur as a result of a current passing through the body, but when an electrical accident causes something to overheat and explode.
Outline how electricity can causes fires?
- Electrical equipment may be faulty, then overheat and results in a fire.
- The system may be overloaded as too much current passes through it, resulting in overheating and fire.
- Equipment may be misused (bare wires into socket rather than plug).
- A flammable atmosphere may be present.
- Electrical equipment may produce heat or sparks as a natural function (a fan heater produces heat).
- Poor internal connections.
List the main risks associated with “Arcing”?
- Electric shock as a result of being struck by the arc.
- Direct burns as a result of being struck by the arc.
- Indirect burns from the radiant heat given off by the arc and from the melting of any equipment.
- Damage to the eye as a result of the ultraviolet (UV) light that is emitted from the arc.