Hello there! I am having difficulty with this question and understanding the dir

Question

Hello there!

I am having difficulty with this question and understanding the directions of current and positive and negatives assigned to the "expert answer posted for this problem. In the text, they say that with resistors, if the direction of current is the same as the direction of the loop then when applying ohms law it will be negative, the text also says that for batteries if the direction of current is the same as the direction as the loop then when applying ohms law it will be positive - the expert answer seems to do the opposite of this.

My other question is - should we not be using the terminal voltage to calculate the current? How does it still come out with a correct answer if we use EMF?

Thank-you so much for your help!

Kathleen

29. (ID (a) What is the potential difference between points a and d in Fig. 19-57 (similar to Fig. 19-13, Example 19-8), and (b) what is the 34 2 h terminal voltage of each battery? 47 2 13 1 2 45 V 182 85 V 1 2 FIGURE 19-57 Problem 29.

Explanation / Answer

your first query: look there are two conventions for it. one you studied in book, is widely accepted and conceptually correct also. concept being if the potential decreases across a element whether battery or resistor. it should be taken negative and if potential increases, it must be taken positive.

but what other expert did is technically wrong but most books also follow that, may be because it is easier to follow for students. thing to note is that we are just reversing the sign of whole equation so answer do not change. e.g. x-y 4 and -x + y = - 4 are same equations

now coming to second query: in the figure, internal resistnace is separately placed (r = 1 ohms) so expert must be counting potential drop across that also. so that means we are using terminal voltage. if you subtract drop across internal resistance from that emf you get terminal voltage

if still a issue let me know.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.