Calculation of equivalent resistance

AI Thread Summary
The discussion focuses on calculating the equivalent resistance between points P and Q in a given circuit diagram. The original poster attempted to solve the problem but arrived at an incorrect answer of (11/10) R, expressing confusion about identifying resistors in series and parallel. Participants suggest numbering the resistors and simplifying the circuit by eliminating unnecessary wires to clarify the configuration. They emphasize the importance of showing detailed workings to identify mistakes and provide accurate guidance. The conversation highlights the need for clear identification of resistor arrangements to solve equivalent resistance problems effectively.
Arka420
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Homework Statement

: [/B]Given the circuit diagram, find the equivalent resistance between points P and Q.
ngodxd.png

Homework Equations

: [/B]ΔVloop = 0, ΔIjunction = 0 and V = IR

The Attempt at a Solution

: [/B]Eliminating the wires with no resistors and solving for resistance gives me the answer as (11/10) R, which is not the answer. I'm confused as to which resistors are in parallel and which resistors are in series.
 
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Perhaps start by numbering the resistors A, B, C etc and post the drawing again.

Tell us which you think are in series or parallel. For example "I think A is in series/parallel with..."

Normally this type of problem is simplified by replacing two resistors in series or parallel with one and redrawing the circuit. You've posted the original so show us the first step/simplification that you made.
 
Arka420 said:

Homework Statement

: Given the circuit diagram, find the equivalent resistance between points P and Q.
ngodxd.png
[/B]

Homework Equations

: ΔVloop = 0, ΔIjunction = 0 and V = IR[/B]

The Attempt at a Solution

: Eliminating the wires with no resistors and solving for resistance gives me the answer as (11/10) R, which is not the answer. I'm confused as to which resistors are in parallel and which resistors are in series. [/B]
Post your working out. We have no way of knowing where you went wrong (and therefore how to help you/ correct any mistakes) if we can't see your reasoning, but the attempt at the problem appears to be right (eliminate the short wire and simplify using the rules for resistors in series/ parallel).
 
Remember also the rule that if multiple resistors have the same voltage drop associated with them then they are parallel
 
This is how I worked out the circuit. Is it correct?
24ex442.png
 
Arka420 said:
This is how I worked out the circuit. Is it correct?
24ex442.png
Not correct.

Follow this advice:
CWatters said:
Perhaps start by numbering the resistors A, B, C etc and post the drawing again.

Tell us which you think are in series or parallel. For example "I think A is in series/parallel with..."
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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