Understanding Resistance and Circuits for Homework Assignments

[peterpan1492]

Homework Statement

My problem is that I don't know how to deal with this kind of questions.

Homework Equations

V=I*R[/B]

The Attempt at a Solution

I thought that the overall resistance would increase since there is a hindrance after the lamp doesn't function anymore, but don't know what to do with the rest...[/B]

 

[Rx7man]

You're on the right track.. yes, total resistance will increase.. Now look at each segment and the change in voltage that will happen from the blown bulb, the change in voltage will of course then affect the amperage through the remaining circuits

 

[peterpan1492]

That is my problem.. I don't know how it will effect the voltage...

 

[Rx7man]

Lets say each lamp is 100 ohm and the supply voltage is 10 v... would you be able to find the voltage potential at the left side of Lamp X? The circuit is basically 1 resistor in series with 2 parallel resistors

So you have 100 ohms in line with 50 ohms (the two parallel resistors together)... If Lamp X blows, you have 100 ohms in line with 100 ohms, right? So resistance increased, thus amperage fell in the system as a whole

 

[peterpan1492]

I am sorry, but it is hard to follow you... the overall resistance increased... how do I now know what happens with ammeter 1 and 2?

 

[Rx7man]

The voltage potential at the 3 way junction (just left of "Lamp X") will change, this will cause a different potential across the two remaining light bulbs and thus a different current through them

 

[peterpan1492]

ok, and why does Ammeter 2 increase?

 

[Rx7man]

because part of the current going to the left lamp is no longer bypassing it through Lamp X... Ammeter 1 and Ammeter 2 are actually in series now and will read the same.

 

[peterpan1492]

and why does ammeter 1 decrease succinctly?

 

[Rx7man]

Because the total resistance of the circuit increased.. If each lamp was 100 ohm for example, the total resistance with Lamp X operational would have been 100 + (100+100)/2 = 150 ohms
after it blew, the resistance of the entire circuit is 200 ohms