aamc 8 #48 terminal voltage

[typicalindian]

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a battery in a circuit has an electromotive force given by 'g' and an internal resistance of 'r'. The battery provides a current i to the circuit. What is the terminal voltage of the battery?

A. g
B. g - ir
C. g + ir
D. g + ir^2

Answer(written in white, highlight it to see): B.

Can someone explain what "terminal voltage" means? I understand that choice B is subtracting the total voltage 'g' that the battery emits from i*r which is the amount of voltage that the circuit is using. But what is terminal voltage?

Also, the solution says this word for word and it doesn't make any sense to me.

 "The battery voltage 1/4 will be reduced by the voltage required to overcome the internal resistance, so V = 1/4 - ir"

I don't understand where they are getting the 1/4 from?

 

[pfaction]

Terminal voltage is the internal resistance of the battery. I have no idea what that's trying to say, but I got it right. G is the absolute max, and IR is what it has to overcome in order to send it out.

 

[typicalindian]

OHHH ok so the i*r described in the passage is the voltage drop due to the actual circuit? and terminal voltage would be the available voltage that could be delivered to components of the circuit? Like resistors and capacitors etc?

 

[folktale]

OHHH ok so the i*r described in the passage is the voltage drop due to the actual circuit? and terminal voltage would be the available voltage that could be delivered to components of the circuit? Like resistors and capacitors etc?

I'm assuming this as well. By the time the original voltage passes the resistor r, it would have a voltage drop equal to ir. "Terminal" voltage would be the voltage after passing that resistor, after the voltage drop. 👍 I missed this question too as well, picked A.

 

[typicalindian]

I'm assuming this as well. By the time the original voltage passes the resistor r, it would have a voltage drop equal to ir. "Terminal" voltage would be the voltage after passing that resistor, after the voltage drop. 👍 I missed this question too as well, picked A.

No I think you have it wrong. The circuit itself takes a certain voltage out of the total voltage. This voltage drop is NOT due to any parts of the circuit, it is actually the circuit itself. The TERMINAL voltage is the voltage that is available to be delivered to the rest of the parts of the circuit AFTER the voltage from the circuit is removed.

 

[folktale]

No I think you have it wrong. The circuit itself takes a certain voltage out of the total voltage. This voltage drop is NOT due to any parts of the circuit, it is actually the circuit itself. The TERMINAL voltage is the voltage that is available to be delivered to the rest of the parts of the circuit AFTER the voltage from the circuit is removed.

Isn't that what I said? Whaaaaat.

 

[typicalindian]

you said "terminal voltage would be the voltage after passing that resistor". I believe terminal voltage IS the voltage that is available to be supplied to that resistor and any other resistors. Unless by "that resistor" you are referring to the circuits internal resistance?

 

[folktale]

you said "terminal voltage would be the voltage after passing that resistor". I believe terminal voltage IS the voltage that is available to be supplied to that resistor and any other resistors. Unless by "that resistor" you are referring to the circuits internal resistance?

I misread r on the question. Yes, by r I meant the internal resistance as stated in the question. Sorry. 😛

 

[fas376]

This question was literally identical to one from TBR physics II.

 

[SaintJude]

The concept of internal resistance is quite popular on MCAT. Will make sure to review "V-IR"

 

[piojita63]

I wrote it on my flashcard like this:
If the BATTERY is supplying current, then: V=E-IR
If the CIRCUIT is supplying current (battery is being charged), then: V=E+IR

Where V is terminal voltage, E is electromotive force, I is current of whole circuit (including internal resistance) and R is the internal resistance.

If you think of it that way (battery receiving or supplying current), it becomes more intuitive.
I hope that helps!
It sure helps me to help you! 😉

 

[folktale]

A. g
B. g - ir
C. g + ir
D. g + ir^2

Answer(written in white, highlight it to see): B.

Can someone explain what "terminal voltage" means? I understand that choice B is subtracting the total voltage 'g' that the battery emits from i*r which is the amount of voltage that the circuit is using. But what is terminal voltage?

Also, the solution says this word for word and it doesn't make any sense to me.

 "The battery voltage 1/4 will be reduced by the voltage required to overcome the internal resistance, so V = 1/4 - ir"

I don't understand where they are getting the 1/4 from?

Regarding the 1/4, I think the 1/4 is not really a numerical value. It is the emf E. Some symbols for some reason are substituted by some weird number or letter throughout the AAMC FLs.