# Science:Math Exam Resources/Courses/MATH152/April 2022/Question B5 (a)/Hint 2

You will have to use Kirchoff’s voltage law, which says that the sum of voltage changes in a loop must equal zero. Note that that in order to use this with the given circuits, you will also need Ohm’s law: if a current flows through a resistance , then the voltage drop across the resistance is .