circuit resistance

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Dec 27th 2010, 11:35 PM
gbenguse78

circuit resistance

1. The problem statement, all variables and given/known data
hi
i am wondering if this is correct. this is the question;
Three cells, each of e.m.f. 1·5 V and internal resistance 0·50 Ω, are connected in series to
make a battery of e.m.f. 4·5V. The battery is connected to a resistor, R, of resistance 6·0 Ω.

2. Relevant equations
V= i/R

3. The attempt at a solution
TOTAL VOLTAGE = 4.5V
TOTAL RESISTANCE = 6.5 OHMS
but the answer states the total resistnace is 7.5 ohms.
can someone kindly explain how?
thanks
Dec 28th 2010, 02:43 AM
BAdhi

when batteries are connected in series the total internal resistance of the batteries can be taken as 3(0.5) so with that and the additional 6, you'll get 7.5
Dec 29th 2010, 10:06 PM
gbenguse78

Quote:

Originally Posted by BAdhi

when batteries are connected in series the total internal resistance of the batteries can be taken as 3(0.5) so with that and the additional 6, you'll get 7.5

apologies for any replies. in crazy exam mode. 8 papers in january! thanks for the hints. its understandable now.