Physics
When a piece of pure silicon is doped with aluminium, then

The doped silicon piece will become p-type
The resistivity of the doped silicon piece will increase
The conductivity of the doped silicon piece will remain the same
The doped silicon piece will become n-type

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

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

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