Physics
In superconductors, the energy gap is due to

Electron-phonon interaction
Electron-photon intercation
Phonon-phonon interaction
Electron-electron interaction

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Physics
A cyclist leans inwards when he is negotiating a curve so that

No frictional force may be produced between the wheels and the axle
Necessary centripetal force may be available from the horizontal component of the normal reaction due to the track to maintain the curved motion.
His weight may be reduced
He may increase his speed

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