Register to reply

D.C circuits PLEASE help...are my answers correct?

by natural
Tags: answers, circuits, correct, helpare
Share this thread:
Feb27-07, 03:47 PM
P: 27
1. The problem statement, all variables and given/known data
To find the emf and internal resistance of an unmarked battery you are given two resistor of value 5.0(ohms) and an ammeter. When the resistors are connected in parallel the current drawn from the battery is 2.0A. What are the e.m.f and internal resistance of the battery?

Am i going right?
2. Relevant equations
E = IR = Ir

3. The attempt at a solution
R = 5(ohms) + 5(ohms) = 10(ohms)

1/R = 1/5 + 1/5 = 2/5
R = 2.5(ohms)

E = 0.75*10 + o.75*r
E = 7.5 + 0.75r ------- (1)

E = 2*2.5 + 2r
E = 5 + 2r ---------- (2)

7.5 + 0.75r = 5 +2r
2.5 = 1.25r
2(ohms) = r

there for r in equation 1 gives
E = 7.5 + 0.75(2)
= 9V
Phys.Org News Partner Science news on
'Office life' of bacteria may be their weak spot
Lunar explorers will walk at higher speeds than thought
Philips introduces BlueTouch, PulseRelief control for pain relief
Feb27-07, 03:49 PM
P: 27
***TYPO****-*********Relavant Equation should be E = IR + Ir*******
Feb27-07, 03:59 PM
berkeman's Avatar
P: 41,320
You didn't include the series combination part in your problem statement. But looking at your work, it would appear that you get 750mA when you connect them in series?

If so, then the rest looks correct.

Register to reply

Related Discussions
Question about tourists that give correct answers and wrong answers. Set Theory, Logic, Probability, Statistics 3
Please verify if my answers are correct. Introductory Physics Homework 2
Probability & QM - pls check whether my answers are correct Calculus & Beyond Homework 7
Organic Chemistry: are these answers correct? Biology, Chemistry & Other Homework 1
All solutions and answers are correct! ! ! General Discussion 47