Ma'anar ƙamus na "caji kowane raka'a" yana nufin adadin cajin wutar lantarki da ke samuwa kowace raka'a na wasu ƙayyadaddun adadi, kamar lokaci, nisa, ko yanki. Ana amfani da wannan kalma sau da yawa a fannin kimiyyar lissafi da injiniyan lantarki don bayyana yadda wutar lantarki ke gudana ta hanyar da'ira, kuma yawanci ana auna ta a cikin raka'a kamar coulombs per second (C/s), coulombs per meter (C/m), ko coulombs per. murabba'in mita (C/m²). Gabaɗaya, cajin kowane raka'a shine ma'auni na yawa ko ƙarfin wutar lantarki a cikin wani tsari ko yanki.