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HYPERCONJUGATION is a phenomenon in organic compounds referring to the delocalisation of sigma electrons. It is also known as sigma-pi conjugation or no bond resonance. It is a permanent effect.

Alkene,Alkynes,Free radicals(saturated),Carbonium ions(saturated).

Presence of alpha-H with respect to the double bond/ triple bond carbon containing +ve charge(for carbonium ion) or unpaired electron(free radicals)

Number of hyperconjugating structures equals the number of alpha-H.

effects of hyperconjugation
It affects the bond length (since during the process the single bond in compound acquires some double bond characters and vice-versa), dipole movement(since it causes the developement of charges) and the stability of free radicals or carbonium ions(which is proportional to the number of hyperconjugating structures).