Problem: Railway electrification system:

The London Underground in England is one of the few networks that uses a four-rail system. The additional rail carries the electrical return that, on third rail and overhead networks, is provided by the running rails. On the London Underground, a top-contact third rail is beside the track, energized at +420v DC, and a top-contact fourth rail is located centrally between the running rails at 210v DC, which combine to provide a traction voltage of 630v DC. London Underground is now upgrading its fourth rail system to 750v DC with a positive conductor rail energised to +500v DC and a negative conductor rail energised to -250v DC. However, many older sections in tunnels are still energised to 630v DC. The same system was used for Milan's earliest underground line, Milan Metro's line 1, whose more recent lines use an overhead catenary or a third rail.

Which system in England is one of the few to use a five-rail system?
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A: unanswerable

Problem: Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠️540 THz (7014540000000000000♠️5401012 Hz). Each photon has an energy E = hf = 6981358000000000000♠️3.581019 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA 7023602200000000000♠️6.0221023 mol1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠️216 kJ/mol, a typical energy of everyday life.
How is the energy from one mole of photos computed?
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Answer: by multiplying the photon energy by the Avogadro constant

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In Theravada Buddhism, the ultimate goal is the attainment of the sublime state of Nirvana, achieved by practicing the Noble Eightfold Path (also known as the Middle Way), thus escaping what is seen as a cycle of suffering and rebirth. Mahayana Buddhism instead aspires to Buddhahood via the bodhisattva path, a state wherein one remains in this cycle to help other beings reach awakening. Tibetan Buddhism aspires to Buddhahood or rainbow body.
In what buddhism is the goal a state of nirvana?
A: Theravada

Context and question: During and after the Greek War of Independence, Greeks of the diaspora were important in establishing the fledgling state, raising funds and awareness abroad. Greek merchant families already had contacts in other countries and during the disturbances many set up home around the Mediterranean (notably Marseilles in France, Livorno in Italy, Alexandria in Egypt), Russia (Odessa and Saint Petersburg), and Britain (London and Liverpool) from where they traded, typically in textiles and grain. Businesses frequently comprised the extended family, and with them they brought schools teaching Greek and the Greek Orthodox Church.
What did they do that contributed to the French's success of establishment?
Answer: unanswerable

Question: Instruction is the facilitation of another's learning. Instructors in primary and secondary institutions are often called teachers, and they direct the education of students and might draw on many subjects like reading, writing, mathematics, science and history. Instructors in post-secondary institutions might be called teachers, instructors, or professors, depending on the type of institution; and they primarily teach only their specific discipline. Studies from the United States suggest that the quality of teachers is the single most important factor affecting student performance, and that countries which score highly on international tests have multiple policies in place to ensure that the teachers they employ are as effective as possible. With the passing of NCLB in the United States (No Child Left Behind), teachers must be highly qualified. A popular way to gauge teaching performance is to use student evaluations of teachers (SETS), but these evaluations have been criticized for being counterproductive to learning and inaccurate due to student bias.
Is there an answer to this question: Teachers don't have to be qualified because of what movement in the US?

Answer: unanswerable

QUES: After many other more or less successful attempts with relatively weak rotating and reciprocating apparatus the Prussian Moritz von Jacobi created the first real rotating electric motor in May 1834 that actually developed a remarkable mechanical output power. His motor set a world record which was improved only four years later in September 1838 by Jacobi himself. His second motor was powerful enough to drive a boat with 14 people across a wide river. It was not until 1839/40 that other developers worldwide managed to build motors of similar and later also of higher performance.

How long did it take for Jacobi's second world record to be broken?
What is the answer?
ANS:
unanswerable