Context and question: Most electrification systems use overhead wires, but third rail is an option up to about 1,200 V. Third rail systems exclusively use DC distribution. The use of AC is not feasible because the dimensions of a third rail are physically very large compared with the skin depth that the alternating current penetrates to (0.3 millimetres or 0.012 inches) in a steel rail). This effect makes the resistance per unit length unacceptably high compared with the use of DC. Third rail is more compact than overhead wires and can be used in smaller-diameter tunnels, an important factor for subway systems.
What depth does the alternating current penetrate in a steel rail?
Answer: skin depth
Context and question: Baptist historian Bruce Gourley outlines four main views of Baptist origins: (1) The modern scholarly consensus that the movement traces its origin to the 17th century via the English Separatists, (2) the view that it was an outgrowth of Anabaptist traditions, (3) the perpetuity view which assumes that the Baptist faith and practice has existed since the time of Christ, and (4) the successionist view, or "Baptist successionism", which argues that Baptist churches actually existed in an unbroken chain since the time of Christ.
What view argues that Baptist churches existed in a broken chain since the time of Christ?
Answer: unanswerable
Context and question: Network hardware, software and specifications, as well as the expertise of network management personnel are important in ensuring that data follows the most efficient route, and upstream connections work reliably. A tradeoff between cost and efficiency is possible.[citation needed]
What follows most inefficient route?
Answer:
unanswerable