Question: Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. Sparks are created by the brushes making and breaking circuits through the rotor coils as the brushes cross the insulating gaps between commutator sections. Depending on the commutator design, this may include the brushes shorting together adjacent sections – and hence coil ends – momentarily while crossing the gaps. Furthermore, the inductance of the rotor coils causes the voltage across each to rise when its circuit is opened, increasing the sparking of the brushes. This sparking limits the maximum speed of the machine, as too-rapid sparking will overheat, erode, or even melt the commutator. The current density per unit area of the brushes, in combination with their resistivity, limits the output of the motor. The making and breaking of electric contact also generates electrical noise; sparking generates RFI. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance (on larger motors) or replacement (on small motors). The commutator assembly on a large motor is a costly element, requiring precision assembly of many parts. On small motors, the commutator is usually permanently integrated into the rotor, so replacing it usually requires replacing the whole rotor.
Is there an answer to this question: What do brushes need to be in contact with?

Answer: commutator


Question: Melbourne is experiencing high population growth, generating high demand for housing. This housing boom has increased house prices and rents, as well as the availability of all types of housing. Subdivision regularly occurs in the outer areas of Melbourne, with numerous developers offering house and land packages. However, after 10 years[when?] of planning policies to encourage medium-density and high-density development in existing areas with greater access to public transport and other services, Melbourne's middle and outer-ring suburbs have seen significant brownfields redevelopment.
Is there an answer to this question: What is generating high demand for housing in Melbourne?

Answer: high population growth


Question: Further desertions of John's local allies at the beginning of 1203 steadily reduced John's freedom to manoeuvre in the region. He attempted to convince Pope Innocent III to intervene in the conflict, but Innocent's efforts were unsuccessful. As the situation became worse for John, he appears to have decided to have Arthur killed, with the aim of removing his potential rival and of undermining the rebel movement in Brittany. Arthur had initially been imprisoned at Falaise and was then moved to Rouen. After this, Arthur's fate remains uncertain, but modern historians believe he was murdered by John. The annals of Margam Abbey suggest that "John had captured Arthur and kept him alive in prison for some time in the castle of Rouen ... when John was drunk he slew Arthur with his own hand and tying a heavy stone to the body cast it into the Seine."[nb 7] Rumours of the manner of Arthur's death further reduced support for John across the region. Arthur's sister, Eleanor, who had also been captured at Mirebeau, was kept imprisoned by John for many years, albeit in relatively good conditions.
Is there an answer to this question: Where was Arthur imprisoned?

Answer: Falaise


Question: Summers in the state are generally hot and humid, with most of the state averaging a high of around 90 °F (32 °C) during the summer months. Winters tend to be mild to cool, increasing in coolness at higher elevations. Generally, for areas outside the highest mountains, the average overnight lows are near freezing for most of the state. The highest recorded temperature is 113 °F (45 °C) at Perryville on August 9, 1930 while the lowest recorded temperature is −32 °F (−36 °C) at Mountain City on December 30, 1917.
Is there an answer to this question: Where was the highest known temperature in Tennessee recorded?

Answer:
Perryville