why is the anode taken as -ve and cathode +ve in an electrochemical cell? why is opposite in the case of a electrolytic cell?
Anode is negative in electrochemical cell. This is because at anode oxidation takes place, during oxidation electrons are released in the reaction which accumulates on the anode and hence it become a negatively charge electrode.
On the other hand, in electrolytic cell electricity is fed to the system in order to carry out a reaction. In this case the two electrode attain opposite charge with respect to the electrodes of electrochemical cell i.e. Anode is +ve and cathode is -ve.
As anode attracts the negatively charge ions i.e. anions therefore it is positively charged electrode and on the other hand cathode attracts cation hence it is negatively charged electrode.