A point labeled J is the only junction in a simplified segment of an electric circuit

PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Circuits · Electric Circuits

Problem

A point labeled J is the only junction in a simplified segment of an electric circuit. Four conductors are connected to J. Two of the conductors carry currents of

3.2\,\text{A}

and

4.8\,\text{A}

toward the junction, while a third conductor carries a current of

6.0\,\text{A}

away from the junction. The current in the fourth conductor,

I_x

, is unknown. Answer the following questions about this situation. (a) State the fundamental physical conservation principle that constrains the possible values of

I_x

at the junction. (b) Use qualitative reasoning (without explicit calculation) to predict whether

I_x

must be directed toward or away from the junction. Justify your answer. (c) Suppose a student mistakenly writes

3.2+4.8+I_x=6.0

and calculates

I_x=-2.0\,\text{A}

. Identify the conceptual error in the student’s setup and explain how the negative sign in the result should actually be interpreted. (d) Write a correct equation relating the four branch currents and determine the magnitude and direction of

I_x

Related theory

Browse the problem library