How Do You Calculate Resistor Values in a Circuit?

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To calculate the resistor values in the given circuit, the battery's emf is 15.0 V, and the terminal voltage is 11.6 V while delivering 20.0 W to an external load resistor R. The equations for Ohm's Law and power (P = VI, P = I²R) are essential for solving the problem. The internal resistance of the battery can be modeled as a resistor in series with the ideal voltage source. A circuit diagram can help visualize the relationship between the external and internal resistances. Understanding these concepts is crucial for determining both the value of R and the internal resistance of the battery.
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Homework Statement


trrttA battery has an emf of 15.0 V. The terminal voltage of the battery is 11.6 V when it is delivering 20.0 W of power to an external load resistor R.
(a) What is the value R?
(b) What is the internal resistance of the battery?


Homework Equations





The Attempt at a Solution


I'm sure how to start this problem. I'm sure I get rolling if I can just get some momentum started. Please Help.
 
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Hopefully these equations will help. If you get stuck just reply.


V = Voltage (Volts)
I = Current (Amps)
R = Resistance (Ohms)
P = Power (Watts)



V = IR (Ohm's Law)

I = V/R (Ohm's Law Rewritten)

P = VI

P = V2/R

P = I2R
 
Last edited:
Keep in mind, the internal resistance of the battery can be modeled as a resistor in series with an ideal voltage source.
 
shinobi12 said:

Homework Statement


trrttA battery has an emf of 15.0 V. The terminal voltage of the battery is 11.6 V when it is delivering 20.0 W of power to an external load resistor R.
(a) What is the value R?
(b) What is the internal resistance of the battery?

Homework Equations



The Attempt at a Solution


I'm sure how to start this problem. I'm sure I get rolling if I can just get some momentum started. Please Help.

Draw a circuit diagram with the external and internal resistor.
You have a voltage divider there don't you?

And you know Power = I2R
 

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