CBSE Class 12 · 2002 · Delhi · Alcohols Phenols and EthersShort Answer

(i) In CH${}_3$OH the full C–O and O–H polarities add up. In phenol the oxygen donates its lone pair into the ring (resonance), creating an opposing charge displacement, and the C(sp${}^2$)–O bond is itself less polar — the vectors partly cancel, so phenol's dipole moment (≈1.54 D) is smaller than methanol's (≈1.71 D).
(ii) The +M donation makes the ring electron-rich, especially at the ortho and para positions — electrophiles (Br${}^{+}$, NO${}_2^{+}$) attack there readily; phenol is far more reactive than benzene in electrophilic substitution.