Electrical Safety Fundamentals

Which legislation established the legal requirement for electrical safety in workplaces?

• AElectricity at Work Regulations 1989✓
• BThe Work at Height Regulations 2005, which cover ladders and scaffolds
• CThe Health and Safety at Work Act 1974, which sets general workplace duties
• DManagement of Health and Safety at Work Regulations 1999

Answer: The Electricity at Work Regulations 1989 is the primary UK legislation requiring electrical equipment to be maintained in safe condition. The other acts are related to broader health and safety but don't specifically address electrical safety.

Who is responsible for ensuring electrical equipment is safe under the Electricity at Work Regulations?

• AThe local authority's building control department alone
• BThe duty holder (employer/person in control)✓
• CThe electrical engineer who installed the equipment
• DThe equipment manufacturer who supplied the appliance

Answer: The duty holder (typically the employer or person in control of the workplace) has the legal responsibility to ensure electrical equipment is maintained in safe working condition.

What does PAT stand for?

• APreventative Appliance Treatment
• BPortable Application Tool
• CPortable Apparatus Testing
• DPortable Appliance Test✓

Answer: PAT stands for Portable Appliance Test. It's the process of inspecting and testing electrical equipment to ensure it remains safe for use.

What is the basic SI unit of electrical current?

• AVolt
• BAmpere✓
• CWatt
• DOhm

Answer: The Ampere (A) is the SI unit of electrical current. Volts measure potential difference, Watts measure power, and Ohms measure resistance.

What is the relationship between voltage, current, and resistance?

• AVoltage = Current + Resistance, so volts equal amps plus ohms
• BVoltage = Current × Resistance (Ohm's Law)✓
• CVoltage = Current / Resistance, so volts equal amps divided by ohms
• DVoltage = Resistance / Current, so volts equal ohms divided by amps

Answer: Ohm's Law states V = I × R (Voltage equals Current multiplied by Resistance). This fundamental relationship is essential for understanding electrical circuit behaviour.

What is an earth fault?

• AA live conductor touching earth or exposed metalwork, so current flows to earth✓
• BA break in the earth wire
• CA loose neutral connection
• DA short circuit occurring between two live conductors, which bypasses the load entirely

Answer: An earth fault occurs when current can flow through an unintended path to earth, creating a potential shock hazard. This is a critical safety concern in PAT testing.

What is the frequency of mains electricity in the UK?

• A60 Hz
• B25 Hz
• C100 Hz
• D50 Hz✓

Answer: UK mains electricity operates at 50 Hz (hertz). The US uses 60 Hz. This frequency affects how electrical equipment is designed and tested.

What is the standard UK mains voltage?

• A250V AC
• B230V AC✓
• C240V AC
• D110V AC

Answer: The UK declared supply voltage is 230V AC between phase and neutral. Regulation 27 of the Electricity Safety, Quality and Continuity Regulations 2002 allows it to vary by up to 10% above or 6% below this, roughly 216V to 253V, so supplies still described as 240V fall within the same declared range.

What is the difference between AC and DC electricity?

• AAC flows in one direction; DC alternates direction
• BDC flows in one direction; AC alternates direction✓
• CDC is the mains supply in UK homes; AC comes from batteries
• DAC is measured in watts, while DC is measured in volts and amps

Answer: DC (Direct Current) flows in one direction from positive to negative. AC (Alternating Current) periodically reverses direction. Mains power is AC; batteries typically provide DC.

What is electrical resistance measured in?

• AVolts
• BAmperes
• COhms✓
• DWatts

Answer: Resistance is measured in Ohms (Ω). One Ohm is the resistance that causes a potential difference of 1 Volt when 1 Ampere flows through it.

What is the purpose of an earth wire in Class I equipment?

• ATo filter out electromagnetic interference generated by the appliance
• BTo provide a low-resistance path to earth for fault current✓
• CTo reduce voltage to the equipment
• DTo carry the mains return current back to the supply during normal operation

Answer: The earth wire provides a low-resistance path for fault current to flow safely to earth, protecting the user from electric shock if a fault develops.

What does the term 'continuity' mean in electrical testing?

• AThat the equipment is able to operate continuously without a break
• BThat the voltage stays constant under load
• CA complete, unbroken electrical path✓
• DThat the current drawn never fluctuates while the appliance runs

Answer: Continuity refers to having a complete, unbroken electrical path. In earth continuity testing, we measure the resistance of the earth circuit to ensure a safe path exists.

What is a potential shock hazard?

• AWhen equipment is plugged in
• BWhen voltage exceeds 50V
• CWhen a person could come into contact with a live electrical conductor✓
• DAny time electricity is present in a room, whether or not conductors are exposed

Answer: A potential shock hazard exists when a person could contact a live conductor. This is what PAT testing aims to prevent through inspection and testing.

What is the definition of 'power' in electrical terms?

• AThe rate at which electrical energy is used (Watts)✓
• BThe resistance offered by a component to the flow of current
• CThe voltage measured across the two terminals of the circuit
• DThe speed at which the current travels along the conductor

Answer: Electrical power is measured in Watts (W) and represents the rate at which energy is consumed. It's calculated as P = V × I (Power = Voltage × Current).

What is insulation in an electrical cable?

• AThe outer protective sheath that guards the cable against abrasion
• BA coating designed to resist heat
• CThe copper conductor which runs down the centre of each core of the cable
• DA material that prevents electrical flow between conductors✓

Answer: Insulation is a non-conductive material that surrounds electrical conductors to prevent current flowing where it shouldn't. Damaged insulation creates a shock hazard.

What is 'leakage current'?

• AThe current that returns to the supply along the neutral wire
• BCurrent flowing to earth through damaged insulation✓
• CCurrent that flows backwards along the live conductor to the supply
• DCurrent that escapes from the pins of the plug into the socket

Answer: Leakage current is unwanted current flowing to earth through deteriorating or damaged insulation. Excessive leakage indicates a potential safety problem.

What is the relationship between power, voltage, and current?

• APower = Voltage + Current
• BPower = Voltage × Current✓
• CPower = Voltage / Current
• DPower = Voltage - Current

Answer: The power formula is P = V × I. For example, a 230V kettle drawing 10A uses 2,300W of power.

What is a conductor in electrical terms?

• AA substance that blocks the flow of electricity through it completely
• BA covering that protects the cable
• CThe person who operates a piece of electrical equipment at work
• DA substance that allows electricity to flow through it✓

Answer: A conductor is a material that allows electrical current to flow through it. Copper and aluminium are common conductors used in electrical wiring.

What is a 'double insulated' appliance?

• AAn appliance with two plugs
• BAn appliance with two cables
• CAn appliance with two layers of insulation and no earth connection✓
• DAn appliance with a metal casing which is bonded directly to the earth pin

Answer: A double insulated (Class II) appliance has two layers of insulation protecting the user and doesn't require an earth wire for safe operation.

Under the IET Code of Practice (5th edition), what is the pass limit for protective conductor current on Class I equipment?

• A15 mA
• B5 mA✓
• C10 mA
• D3.5 mA

Answer: The 5th edition (2020) sets a single limit of 5 mA for protective conductor current on Class I equipment and for touch current on Class II. The 4th edition's tiered limits, such as 3.5 mA for most Class I items and 0.75 mA for hand-held ones, no longer apply, although some product standards and tester presets still use lower figures.

What is a 'fault current'?

• AThe current carried by the live wire
• BCurrent that occasionally fluctuates as the load on the circuit changes
• CUnwanted current flowing due to a fault in the equipment✓
• DThe normal running current drawn by a device that has stopped working

Answer: A fault current is unwanted current that flows when equipment develops a fault, such as a breakdown of insulation allowing current to flow to earth.

What is the purpose of earthing in electrical systems?

• ATo increase the amount of current flowing through the appliance
• BTo provide a safe path for fault current to reach earth✓
• CTo prevent the appliance from overheating during long periods of use
• DTo reduce the supply voltage to the appliance

Answer: Earthing provides a safe, low-resistance path for fault current to flow to earth, protecting people from electric shock by limiting voltage.

What does 'impedance' mean in electrical terms?

• ATotal opposition to current flow in an AC circuit✓
• BThe voltage measured between the live and neutral conductors
• CThe power consumed by an appliance while it is running normally
• DResistance alone, with no reactance being taken into account

Answer: Impedance is the total opposition to AC current flow, including both resistance and reactance. It's measured in Ohms.

What is the standard earthing conductor colour in the UK?

• ABlack
• BRed
• CBlue
• DGreen/Yellow striped✓

Answer: The earth conductor is coloured green and yellow striped (or sometimes just green in older installations). This is standardised across UK electrical installations.

What is electrical 'resistance' in a wire?

• AThe thickness of the wire measured across its diameter
• BThe opposition to electrical current flow✓
• CThe overall length of the wire measured from end to end
• DThe ability of a wire to store electrical charge for later use

Answer: Resistance is the opposition to electrical current flow. All materials have some resistance; it's measured in Ohms and causes heat generation as current flows.