Variable Resistor connected to parallel resistors

AI Thread Summary
The discussion revolves around solving a physics problem involving a variable resistor and parallel resistors in an electric circuit. When the variable resistor R3 is set to 25Ω, the current into the power supply is 2A, and at 5Ω, the current through R2 is 1A. Participants discuss calculating the combined resistance of R1 and R2, finding the value of R2, and determining the power consumed by R1 when R3 is 25Ω. Clarifications about the voltage across the resistors and the nature of variable resistors are provided, leading to a breakthrough in understanding for one participant. The conversation emphasizes the importance of applying Ohm's Law and the formula for parallel resistance in solving the problem.
ordem
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Homework Statement


In the electric circuit shown in the figure, when the value of the variable resistor R3 is 25Ω, the current which flows into the power supply is 2A. Moreover, when the value of the variable resistor R3 is 5Ω a current of 1A flows into the resistance R2.
der879.gif


Q1.Find the value of parallel combined resistance of resistance R1 and R2,
Q2.Find the value of R2,
Q3.When the resistance R3 is 25Ω how much electric power is consumed by resistance R1

Homework Equations


V=IR
R parallel combined =( R1 x R2) / (R1 + R2)

The Attempt at a Solution


from the first given information i know that the volt at R3 is 50 then the volt at combined resistance is 30 then I tried various equations but then I stuck ,please help me this is the first time I met a physics problem with variable resistor, what is it really?
 
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ordem said:
from the first given information i know that the volt at R3 is 50 then the volt at combined resistance is 30 then I tried various equations but then I stuck

Hi ordem. Welcome to Physics Forums.

In addition to carrying 30 volts, you also know that the current through the parallel combination is 2 amps. Can you now determine the resistance of that parallel combination? :wink:

A variable resistor is one whose resistance can be set to a different value.
 
OH MY GOD, thank you so much for the answer, as soon as I read what you wrote, I feel so stupid, now I know all the answers , i don't know what hit my head before, haha, thanks again
 
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