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WorksheetsVolt Drop
Total questions: 11
Worksheet time: 15mins
What is the formula for calculating voltage drop according to the text?
Voltage Drop = L x Ib / (mV/A/m)
Voltage Drop = Ib / (mV/A/m) x L
Voltage Drop = (mV/A/m) + Ib + L
Voltage Drop = (mV/A/m) x Ib x L / 1000
Where can you find the value for (mV/A/m) needed to calculate voltage drop?
Appendix A of the OSG
Appendix H of the OSG
Appendix F of the OSG
Appendix Z of the OSG
What does 'Ib' represent in the voltage drop calculation?
The design current
The length of the circuit
The voltage of the circuit
The resistance of the circuit
How is the design current (Ib) usually calculated?
Voltage divided by resistance
Voltage times current
Watts divided by voltage
Current times resistance
What does 'L' represent in the voltage drop calculation?
The length of the circuit in metres
The load of the circuit in watts
The luminosity of the circuit
The lag of the circuit in seconds
For which systems does BS7671:2018 not provide voltage drop values?
Overhead cable systems
Underground cable systems
Power track and lighting trunking systems
Domestic lighting systems
What is the voltage drop for a multi-core 70 degrees C thermoplastic non-armoured cable with 2.5 mm conductors supplying a single-phase load of 20 amp at 230 volts over 22m?
10.00V
9.00V
8.22V
7.92V
Where in the BS7671:2018 can you start looking for the current carrying capacities and voltage drop for cables?
Appendix A
Table of tables on page 522
The glossary
Chapter 5
What is the correct table in the OSG for finding the voltage drop of a 70 degrees C thermoplastic flat cable with protective conductor non-armoured cable with 2.5 mm conductors?
Table E3
Table F6
Table F3
Table A2
What is the value of (mV/A/m) for a 2.5 mm sq conductor of a multi-core 70 degrees C thermoplastic non-armoured cable?
18 mv/A/m
24 mv/A/m
20 mv/A/m
22 mv/A/m
What cable size would be required for a 45m run of a pair of single core 70 degree thermoplastic cables with a design current of 14A installed reference B on a power radial?
1.5mm
2.5mm
4mm
6mm
