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1. The figure shows a section of a circuit. The resistances are R 1 = 2.1 ?, R 2

ID: 581325 • Letter: 1

Question

1. The figure shows a section of a circuit. The resistances are R1 = 2.1 ?, R2 = 5.0 ?, and R3 = 6.9 ?, and the indicated current is i = 6.5 A. The electric potential difference between points A and B that connect the section to the rest of the circuit is VA - VB = 79 V. (a) Is the device represented by “Box” absorbing or providing energy to the circuit, and (b) at what rate?

2.

In the figure ? = 13.3 V, R1 = 2580 ?, R2 = 2330 ?, and R3 = 4490 ?. What are the potential differences (in V) (a)  VA - VB, (b)  VB - VC, (c)  VC - VD, and (d)  VA - VC?

R2 WBox Box Rg

Explanation / Answer

(1) Potential difference about R3 = 6.5*6.9 = 44.85 Volt
potential drop in R1 = 79 -44.85 = 34.15 volt
Current in R1 = 34.15 / 2.1 = 16.262 A
Current in R2  = 16.262 - 6.5 = 9.76 A
potential drop in R2 = 9.76*5= 48.809 Volt
but drop should be 44.85 volt only because it is in parallel with R3
therefore box is providing energy .
the voltage provided by the box will be = 48.809 - 44.85 = 3.96 volt