Current flowing from point A in a circuit to point B

AI Thread Summary
A current of 2A flows from point A through a 3-ohm resistor, a 20V battery (negative terminal first), a 1-ohm resistor, and a 6V battery (positive terminal first). The potential difference between points A and B is influenced by the voltage drops across the resistors and the voltage rises through the batteries. It is clarified that when current flows through a resistor, the side entering the resistor is at a higher potential than the side exiting. The discussion emphasizes the importance of correctly accounting for voltage rises and drops in the circuit. Point B is identified as the negative terminal of the 6V battery, which is crucial for calculating the potential difference accurately.
FADFAD1

Homework Statement


A current at point A of 2A flows through a resistor (3 ohms), a battery of 20V (negative terminal first), another resistor (1 ohm) and a battery of 6V (positive terminal first). What is the potential difference between A and B

Homework Equations

The Attempt at a Solution


I used a negative voltage for when it passes through the first resistor then added 20V through the battery but it doesn't seem right
 
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I think you are correst.
I would say that a current of 2A flows from the rest of the circuit through point A into the 3Ω resistor. Point A has to be more positive than the other side of this resistor to make such a current flow.
 
FADFAD1 said:
I used a negative voltage for when it passes through the first resistor then added 20V through the battery but it doesn't seem right

That is 100% correct. Just keep going. So far you have..

-(2*3) + 20 ...
 
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Likes Asymptotic and scottdave
It might help if you draw the circuit, labeling the voltage drops (or rises) for each device.
You said you did not get the correct answer. (actually you said it doesn't seem right, sorry).
What answer did you get? How did you arrive at that answer? If we can see that, then we can better guide you to where the mistake is.

If current flows through a resistor from left to right, then the left side will be at higher (more positive) potential than the right. Flow through a battery depends on the polarity of the battery. If it goes from negative terminal (through the battery) to positive, then it is a voltage rise.
 
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What is point B?
 
Asymptotic said:
What is point B?
It sounds like B is the negative terminal of the 6 volt battery.
 
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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