A battery-battery-resistor circuit

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In summary, the conversation discusses a circuit with two batteries and a lamp, where the circuit is producing 0.25 Watt to the lamp. The question is what is the inside-resistance of the batteries? The solution involves finding an expression for power consumption in the lamp and solving for the current, rather than assuming the voltage across the lamp is 3V.
  • #1
zimo
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Homework Statement


A circuit:
Battery (1.5v) -- Battery (1.5v) -- Lamp(18 Ohm) and back to the first battery.

The circuit is producing 0.25 Watt to the lamp. what is the inside-resistance of the batteries?

Homework Equations


P=VI
IR=V

The Attempt at a Solution


1.5+1.5=3Volt
P=0.25Watt
0.25=3*I
I=1/12
(1/12)*R=3
R=36
we already have 18 Ohms from the lamp so the remining 36-18=18 is the answer.
WRONG:confused:
 
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  • #2
You cannot assume that the voltage across the lamp is 3V--not when the batteries have internal resistance. Instead, find an expression for power consumption in the lamp in terms of I and R, and solve for the current.
 
Last edited:
  • #3
Oh, I got it now, Thanks!
 

1. What is a battery-battery-resistor circuit?

A battery-battery-resistor circuit is a type of electrical circuit that uses multiple batteries and a resistor to control the flow of electric current.

2. How does a battery-battery-resistor circuit work?

In this circuit, the batteries provide the electrical energy while the resistor restricts the amount of current that can flow through the circuit. This allows for the controlled use of the batteries' energy.

3. What is the purpose of using a resistor in this circuit?

The resistor in a battery-battery-resistor circuit acts as a load or a resistance to the flow of current. This helps to prevent the batteries from supplying too much current and potentially damaging the circuit.

4. What are the advantages of using a battery-battery-resistor circuit?

This type of circuit allows for better control and regulation of the current, which can help to prolong the lifespan of the batteries and prevent damage to the circuit. It also allows for a more efficient use of the batteries' energy.

5. How can the resistance of the resistor be determined in a battery-battery-resistor circuit?

The resistance of the resistor can be calculated using Ohm's Law, which states that resistance is equal to voltage divided by current. By knowing the voltage of the batteries and the desired current, the appropriate resistor can be chosen.

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