Posted by ALan on Wednesday, February 10, 2010 at 12:07am.
A resistor has a resistance R, and a battery has an internal resistance r. When the resistor is connected across the battery, ten percent less power is dissipated in R than would be dissipated if the battery had no internal resistance. Show that the ratio r/R is equal to 0.054
I let R = 1 ohms
r 0.054 ohms
*Without Internal resistance*
Vloop=0
emfIR=0
emf=IR
*With internal resisntace*
Vloop=0
emfIRIr=0
emf=IR+Ir
I get stuck after this, I am unsure where to head now. Can someone please write out the procedure? Please and thank you.

Phyics  drwls, Wednesday, February 10, 2010 at 1:09am
P1 = V^2/R is the power dissipated in R with no internal resistance.
With internal resistance r, the current is V/(R+r) and the power dissipated in R is
P2 = I^2*R = V^2*R/(R+r)^2
If P2/P1 = 0.9,
R^2/(R+r)^2 = 0.9
R/(R+r) = 0.9487
(R+r)/R = 1 + r/R = 1.054
r/R = 0.054

Phyics  ALan, Wednesday, February 10, 2010 at 11:16am
Thanks a lot!
Answer This Question
Related Questions
 Ap physics  Four resistors are connected to a battery with a terminal voltage ...
 Physics  A battery with an emf of 7.9 V and internal resistance of 1.37 Ω...
 physics  Consider a battery that has Vt = 12.0 V when it is not connected to a ...
 physics  A resistor of resistance R is connected to a power supply of constant ...
 physics  when you connect an unknown resistor across the terminals of a 1.50 V ...
 physics  hen a battery is connected to a 100Ω resistor, the current is 4....
 Physics  A 79.4Ω and a 47.7Ω resistor are connected in parallel. ...
 physics  when a battery is connected to a 100Ω resistor, the current is 4...
 Physics  a)In the series circuits, what do you notice about the voltage across ...
 Physics  A battery delivering a current of 55.0 A to a circuit has a terminal ...
More Related Questions