Current and Current Density at a Junction The magnitudes of the current density

Question

Current and Current Density at a Junction The magnitudes of the current density and the diameters for wires 1 and 2 are given in the table. The current directions are indicated b y the arrovw Consider the juncion of three wires as shown in the diagram. (Figure 1) Current density (A/mm2) 3.2 5.2 Diameter (imm) 1.9 2.4 Wire Part A Find the current I3 in wire 3 Express your answer in amperes to two significant figures. Call current out of the junction positive and current into the junction negative Hints Figure 1 Submit My Answers Give Up Part B Wire 1 This question will be shown after you complete previous question(s) Wire 2 ovide Feedbac Continue Wire 3

Explanation / Answer

current = current density x cross sectional area

I1 = (3.2)(pi (1.9/2)^2) = 9.07 A

I2 = (5.2)(pi (2.4/2)^2) = 23.5 A

Applying KCL at junction,

I2 - I1 + I3 = 0

23.5 - 9.07 + I3 = 0

I3 = - 14.4 A

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