Current in a circuit Defined to be opposite direction of the flow of electrons
Current in a circuit Electrons move in opposite direction I
Kirchoff’s 1 st Rule Junction rule. The sum of the currents entering a junction equals the sum of the currents leaving the junction. Conservation of… charge.
Kirchoff’s 2 nd Rule Loop rule. The net change in electrical potential in going around one complete loop in a circuit is equal to zero. Conservation of energy.
AP Circuit Analysis Unlike the Regents, the AP exams and college textbooks; 1) define current as the flow of + charge 2) have mixed circuits that with series and parallel elements 3) can have capacitors 4) can have more than one battery 5) the batteries aren’t necessarily ideal; they can have internal resistance that reduces voltage output 6) you may need to use a loop rule to figure out voltage drops
Through resistors: Going with the current is like going downhill, negative V, Going against current is like going uphill, + V. Voltage Drops When doing a loop analysis, V =0. Some V are +, some -. Through batteries, going from – to + is an increase, or + V. going from + to - is logically a loss of potential or - V.
Applying Kirchhoff’s Laws Goal: Find the three unknown currents. Using Kirchhoff’s Voltage Law First decide which way you think the current is traveling around the loop. It is OK to be incorrect. Using Kirchhoff’s Current Law
Applying Kirchhoff’s Laws A NEGATIVE current does NOT mean you are wrong. It means you chose your current to be in the wrong direction initially. -0.545 A