Electrical Safety

What is the primary hazard of electricity?

• AOnly the colour of the cable insulation used
• BElectric shock causing injury or death✓
• CThe noise made by the electrical equipment
• DOnly the smell given off by the hot cables

Answer: Electric shock is the primary hazard. Electricity can cause cardiac arrhythmia, respiratory paralysis, burns, and death. Even low voltages can be lethal under certain conditions.

What is the 'safe voltage limit' for 50V AC in the UK?

• AAbove 50V AC becomes hazardous; lower voltages are safer but not necessarily safe✓
• B50V is never dangerous
• CAnything below 50V is safe
• DOnly very high voltages such as 400V and above are dangerous to a person working on site

Answer: While 50V AC is generally safer than higher voltages, it can still cause electric shock under certain conditions (wet conditions, contact area, individual factors). BS 7671 recommends extra-low voltage for certain situations.

What are the main routes of electrical current entry to the body?

• AOnly through cuts, because intact skin will always stop the current flowing
• BContact with live parts; hand-to-hand, hand-to-foot, or foot-to-foot paths✓
• COnly the eyes
• DOnly through broken skin such as a cut or a graze on the hands or the forearms

Answer: Current enters through contact with live parts, with dangerous paths including: hand-to-hand (across the chest, affecting heart), hand-to-foot, and foot-to-foot paths.

What is an 'arc flash'?

• AA regular spark
• BLightning in the sky during a storm, which can travel down a supply cable into a building on site
• CA safety device
• DDangerous electrical event with intense heat and light from arcing between live conductors✓

Answer: Arc flash is a dangerous electrical event where current jumps across a gap (arc), producing intense heat (>3000°C), light, pressure, and hot metal spray that can cause severe burns.

What does 'earthing' do in an electrical system?

• AIt is what makes the electricity flow round the whole of the final circuit
• BIt is only there to give lightning a path to earth during a thunderstorm
• CProvides a return path for fault current and reduces electric shock risk✓
• DStops electricity

Answer: Earthing (grounding) provides a safe path for fault currents to earth, reducing the voltage experienced by a person in contact with an energized object.

What is 'double insulation' in electrical equipment?

• AUsing two plugs so that the equipment always has a spare supply
• BTwo layers of insulation preventing contact with live parts✓
• CTwo complete sets of wires running to the same piece of equipment
• DExtra heavy cables fitted with a thicker outer sheath than normal

Answer: Double insulation provides two independent layers of insulation (functional and protective) so that if one breaks down, the second prevents contact with live parts.

What is a Residual Current Device (RCD)?

• AA safety device that detects current imbalance and disconnects the circuit quickly✓
• BA resistor
• CA type of wire with a larger cross-section, used where the circuit carries a heavy load
• DAn insulator

Answer: An RCD (earth leakage breaker) detects any imbalance between live and neutral currents (indicating current to earth) and trips the circuit within milliseconds, preventing serious shock.

What is BS 7671?

• AThe IET Wiring Regulations - UK standard for safe electrical installation design and installation✓
• BAn electrical component fitted inside a consumer unit, which the manufacturer supplies with its own instructions
• CA cable type
• DA voltage rating

Answer: BS 7671:2018 (Requirements for Electrical Installations) is the UK standard for the design, selection, installation, inspection and testing of electrical systems.

What does 'isolation' mean in electrical safety?

• ASwitching the equipment off at the local switch and leaving a note on it to say that work is in progress
• BUnplugging a device
• CSeparating equipment from live parts by creating a physical barrier or disconnecting from supply✓
• DTurning off the lights

Answer: Isolation is the safe separation of electrical equipment from all live parts by physical isolation (barriers, covers) and/or electrical isolation (disconnection from the supply).

What is 'lock off tag out' (LOTO)?

• AProcedure of isolating equipment and preventing accidental energization by locking disconnects and applying warning tags✓
• BOnly for padlocks
• CJust a label
• DLocking tools and equipment away in the site store at the end of the shift so that nobody can use them overnight without permission

Answer: LOTO involves isolating equipment from energy sources and using physical locks and warning tags to prevent unexpected startup while work is being carried out.

What should be done before working on electrical equipment?

• AAsk the person who fitted the equipment whether it is safe, and take their word for it
• BOnly if in a hurry
• CJust dive in
• DIsolate from supply, lock off, test the circuit is de-energized, use appropriate PPE✓

Answer: Safe procedure: Isolate the equipment, lock and tag the isolator, test with a voltage tester to confirm de-energization, and only then proceed with work using proper PPE.

What is a 'live working permit'?

• ADiscretionary
• BAny written authorisation to start work, whether the equipment is live or has been isolated
• CFormal authorization to work on energized electrical equipment under strict procedures✓
• DA driving license

Answer: A live working permit formally authorizes and documents work on live electrical parts, requiring competent personnel, additional controls, and strict procedures to minimize shock risk.

What is the correct way to test that a circuit is de-energized?

• ATouch the conductors with the back of your finger to feel for a tingle
• BJust assume it's safe
• CUse a proper voltage tester/multimeter to confirm no voltage present✓
• DAsk the person who isolated it whether it is safe to touch the conductors

Answer: Always use a properly functioning voltage tester or multimeter to confirm absence of voltage. Test the tester first on a known energized source to verify it works.

What is 'overhead line clearance' distance?

• AMinimum safe distance to maintain from overhead power lines (typically 6-8 metres)✓
• BOnly matters if raining
• CJust don't touch the line
• DAny distance away from the line, as long as nothing metal is being carried above head height

Answer: Overhead power lines have minimum clearance distances to prevent electrocution risk. Electrically conductive items (cranes, ladders) must stay 6-8 metres away depending on voltage.

What hazards exist when working on electrical distribution boards?

• AThere are no hazards once the main switch on the board has been turned off
• BOnly heat
• COnly the noise made by the contactors and breakers inside the board
• DElectric shock, arc flash, confined space hazards if in enclosures✓

Answer: Distribution boards present risks of shock from live parts, arc flash if a fault occurs, and potentially confined space hazards. Proper PPE and isolation procedures are essential.

What is the purpose of an 'insulated tool' in electrical work?

• AIt serves no particular purpose beyond comfort in the hand when working
• BIt just feels better in the hand than a standard uninsulated tool
• CTo reduce shock risk by preventing current path through the body✓
• DTo make the work go faster by improving the grip on the fixings used

Answer: Insulated tools provide a barrier between the worker and live parts, reducing the risk of electric shock if the tool contacts a live conductor accidentally.

What is 'temporary bonding' in electrical safety?

• AUnimportant
• BJust decorative wiring
• CUsing temporary wires to feed power to tools while the permanent supply is being installed
• DTemporary connection of conductive parts to ensure they are at the same potential✓

Answer: Temporary bonding electrically connects exposed conductive parts to the same potential, preventing dangerous potential differences and arcing between parts.

What should you do if someone receives an electric shock?

• APull them away from the equipment immediately with your bare hands before anything else
• BSwitch off supply first if safe, then provide first aid, call emergency services✓
• CLeave them alone
• DLeave the casualty where they are and go off site to find help for yourself first

Answer: On discovering an electrical shock victim: switch off the supply (if safe), or break contact using non-conducting material, provide CPR/first aid, and call emergency services.

What is a 'permit to work' system for electrical work?

• ADispensable
• BFormal authorization system documenting risk assessment, isolation steps, and precautions for work on electrical equipment✓
• CJust a verbal agreement between the electrician and the supervisor that the work can go ahead, recorded in the site diary afterwards
• DPermission slip from home

Answer: A permit to work for electrical tasks documents: identified hazards, isolation measures, lock-off procedures, testing confirmation, rescue arrangements, and authorized personnel.

What is an 'electrical test certificate'?

• AA qualification
• BA diploma
• CDocumentation confirming that electrical installation or equipment has been properly tested and meets safety standards✓
• DJust a piece of paper handed over at the end of the job, with no legal or technical meaning attached to it at all whatsoever

Answer: An electrical test certificate documents the results of periodic inspection and testing of electrical installations, confirming safety standards are met and no faults exist.

What is 'earth fault loop impedance' (EFLI)?

• AA transformer fitted at the origin of the installation to reduce the supply voltage before it reaches the circuits
• BJust a test
• CA type of cable
• DThe impedance of the path for earth fault current, affecting shock protection effectiveness✓

Answer: EFLI is the total impedance in the earth fault path, measured during testing. Lower EFLI means faster fault clearance and better protection against electric shock.

What protection is provided by a circuit breaker?

• AOnly for lightning
• BAutomatically disconnects supply when current exceeds safe levels, preventing overheating and fire✓
• COnly during storms
• DIt simply breaks the circuit by hand when someone wants to work on it, and gives no protection at all

Answer: Circuit breakers automatically disconnect the circuit if current exceeds design limits, protecting against overcurrent, short circuits, and the resulting overheating and fire risk.

What is 'competency' for electrical work?

• ALuck and quick thinking
• BHaving adequate knowledge, skills, training, and experience to work safely with electricity✓
• CHaving finished enough electrical jobs to be quick at the work, whatever training has been done
• DJust having a tool kit

Answer: Electrical competence requires: relevant qualifications, training in safety procedures, understanding of BS 7671, experience with similar work, and demonstrated practical ability.

What should be included in an electrical safety briefing for workers?

• AHazards, safe procedures, isolation requirements, emergency arrangements, and specific work precautions✓
• BIt only needs giving when management remembers to arrange one, since the method statement already covers the detail
• CJust tell them to be careful
• DWritten material only

Answer: A briefing should cover: specific hazards of the task, required safety procedures, isolation and lock-off arrangements, emergency procedures, and rescue arrangements.

What is 'thermal burn' in the context of electrical injury?

• ABurn caused by heat from electrical current or arc flash✓
• BSunburn picked up while working outdoors on a hot summer day
• CA minor injury that is not dangerous and needs no treatment
• DA burn that can only be caused by open flames or hot surfaces

Answer: Thermal burns result from the heat generated by electrical current passing through tissue or from arc flash. They can be severe and deep, causing tissue damage.