Arrange bulbs in descending order of brightness

[Jahnavi]

Homework Statement

Homework Equations

The Attempt at a Solution

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Sorry for the messy image .

I have got the right answer by assuming certain values of the resistors . But I would like to know whether this question can be done logically without assigning numerical values to the resistors .

Initially when S2 is open and S1 is on position 2 , all the resistors are in series .Same current flows through them . The one with higher resistance will have higher power dissipated and will flow brighter .From this I concluded R2>R1>(R3=R4) .

Now S2 is closed and S1 is on position 1.This makes R2 in parallel with R1 .

Now I assigned some numbers to the resistors such that R2>R1>(R3=R4) and checked the respective i²R values .Then compared it with their initial i²R values .

Could someone suggest an alternative/faster approachwhuch requires lesser calculation to solve this problem .

Thanks

 

[cnh1995]

1.This makes R2 in parallel with R1**R3 .

Now I assigned some numbers to the resistors such that R2>R1>(R3=R4) and checked the respective i2R values .Then compared it with their initial i2R values .

In the new circuit, current is same for two bulbs (B1 and B4).
Which is brighter?

B3 will receive less current than B4 and R3=R4.
Which is brighter?

Voltage across B2 and B3 is same, but R2>R3.
Which is brighter?

What is the descending order then?

 

[Jahnavi]

Wow ! Impressive reasoning

Exactly what I was looking for .

You have taught me a very nice way to think in such type of problems .



Thanks a lot !

 

[K6noteJordan]

Wow ! Impressive reasoning

Exactly what I was looking for .

You have taught me a very nice way to think in such type of problems .



Thanks a lot !

Thanks for giving me a new logic .you made my day