Unit 16 - ELT 604 (Practice CBT)

What is the effect on an installation forming part of an MEN system if the PEN conductor develops a high impedance?

• Voltage will appear on earthed metalwork.

• Installation neutral conductor will overheat.

• Protective devices will operate more quickly under fault conditions.

• Voltage will only appear on earthed metalwork if an earth fault occurs.

Which parts of an electrical installation are connected by the earthing conductor?

• Exposed conductive parts and main earthing terminal.

• Main earthing terminal and earth electrode

• Two extraneous conductive parts.

• No connection needed

What is the purpose of equipotential bonding?

• To earth an exposed conductive part.

• To earth the metal casing of Class I equipment.

• To provide a conducting path in the event of an earth fault.

• To keep two exposed Conductive parts at or about the same potential.

What factor affects the value of earth fault loop impedance of a circuit?

• Resistance of the neutral conductor.

• Type of cable insulation.

• Rating or the circuit protective device.

• Length of circuit cable.

What is the maximum residual operating current of an RCD that provides protection against contact with live parts?

• 10 mA

• 30 mA

• 100 mA

• 300 mA

Which method may be used to safeguard an installation against overvoltage?

• Fit a surge protective device at the main terminals.

• Connect the installation to an overhead distribution system.

• All appliances rave an impulse withstand voltage of 6 kA.

• Installation has a main fuse or circuit breaker which disconnects the maximum fault current.

What action must be taken when carrying out a visual inspection of a new electrical installation?

• Installation must be totally isolated from the supply.

• All testing must be carried out before the inspection starts.

• Only the wiring and control equipment is inspected.

• All cables are inspected throughout their length.

What insulation resistance test voltage be used when testing a 220 V circuit?

• 250 V

• 380 V

• 500 V

• 1000 V

Which measure provides protection against direct contact?

• electrical separation

• barriers and enclosure

• non-conducting location

• automatic disconnection of supply

What is the minimum recognized shock current likely to cause muscular contraction?

• Approximately 5 mA

• Approximately 10 mA

• Approximately 20 mA

• Approximately 30 mA