Write is a salt bridge ? What is it used for ?

Explanation

A salt bridge is a U - shaped tube containing concentrated solution of an inert electrolyte like `KCl, KNO_3, K_2SO_4`, etc., or a solidified solution of an electrolyte such as agar-agar and gelatine. It is used,
(i) To complete the electrical circuit by allowing ions to flow from one solution to the other without mixing the two solutions .
(ii) To maintain the electrical neutrality of the solutions in the two half cells.