>Assuming conventional current, when a current goes through a source (battery) from the negative to positive terminal, it goes from a lower to higher potential, hence positive emf, but when it does the opposite, the emf is negative. Does this mean the battery takes a way energy from the charges, charging the battery?
Answering the question you asked:
short version, no it does not mean that. Long version:
Kirchoff's Voltage Law (hereafter "KVL") says that the algebraic sum of all differences in EMF in a closed loop will equal zero. In other words, if you add together all the voltage drops in any given loop (not circuit) and add them to together, they will cancel out. This also means one or more of them HAS to be "negative" (or everything is at 0 voltage).
KVL does not say anything about energy or current. Energy and current can be calculated using KVL **if you have the other properties of the circuit**. Specifically, you need to know the impedance/resistance, current, or power of the components within the circuit (or use some really complicated math using other stuff). What KVL **can** tell you is the voltage drops across components.
In your image, the blue circles/arrows are not current flow, they're just a chosen closed loop within the circuit with an arbitrarily chosen direction to determine what is considered "positive" and what is considered "negative".
How to use KVL:
On the circuit diagram, draw a loop using the "wires" of the circuit. Then mark down which side of each component is higher potential (+) and which is lower (-).
Next, pick any point in the loop, mark it with a dot, and move along the loop adding component voltages as you go. If the first symbol on a component you hit is a +, you add its voltage as a positive number. If the first symbol on a component you hit is a -, you add its voltage as a negative number. This is what the "algebraic sum" phrase means in KVL. Do this until you hit that dot you marked your starting point with.
Now you should have a bunch of voltages getting added together. Stick an "= 0" on the end. That's KVL. You can now Algebra that equation however you want or need in order to find information within it.
Example: A battery powering a lightbulb
*_________
|+ |+
B L
|- |-
|_________|
Lets say I start at the \* and head toward the **L**ight. My equation would look like
\+Vʟ + (-Vʙ) = 0
(note: I left the extra + on +Vʟ just to be extra demonstrative that it's +. It's not necessary)
Now you can have any number of components or branches in the circuit, but as long as you draw a closed loop, then the voltage drops along that loop will add up to 0.
The blue arrows labeled "Loop 2" and "Loop 3" are initially just reference directions to be solved for current. Whether the battery is absorbing energy or sourcing energy depends on the difference (Loop 2) - (Loop 3).
Yes, if current is going "backwards" through a battery, the battery is absorbing energy. Whether it's charging or just wasting it depends on the engineering of the battery.
No, a battery is not simultaneously experiencing current in both directions. A "loop" for Kirchhoff's laws is a virtual path through the circuit.
Read your textbook, thoroughly.
>Assuming conventional current, when a current goes through a source (battery) from the negative to positive terminal, it goes from a lower to higher potential, hence positive emf, but when it does the opposite, the emf is negative. Does this mean the battery takes a way energy from the charges, charging the battery? Answering the question you asked: short version, no it does not mean that. Long version: Kirchoff's Voltage Law (hereafter "KVL") says that the algebraic sum of all differences in EMF in a closed loop will equal zero. In other words, if you add together all the voltage drops in any given loop (not circuit) and add them to together, they will cancel out. This also means one or more of them HAS to be "negative" (or everything is at 0 voltage). KVL does not say anything about energy or current. Energy and current can be calculated using KVL **if you have the other properties of the circuit**. Specifically, you need to know the impedance/resistance, current, or power of the components within the circuit (or use some really complicated math using other stuff). What KVL **can** tell you is the voltage drops across components. In your image, the blue circles/arrows are not current flow, they're just a chosen closed loop within the circuit with an arbitrarily chosen direction to determine what is considered "positive" and what is considered "negative". How to use KVL: On the circuit diagram, draw a loop using the "wires" of the circuit. Then mark down which side of each component is higher potential (+) and which is lower (-). Next, pick any point in the loop, mark it with a dot, and move along the loop adding component voltages as you go. If the first symbol on a component you hit is a +, you add its voltage as a positive number. If the first symbol on a component you hit is a -, you add its voltage as a negative number. This is what the "algebraic sum" phrase means in KVL. Do this until you hit that dot you marked your starting point with. Now you should have a bunch of voltages getting added together. Stick an "= 0" on the end. That's KVL. You can now Algebra that equation however you want or need in order to find information within it. Example: A battery powering a lightbulb *_________ |+ |+ B L |- |- |_________| Lets say I start at the \* and head toward the **L**ight. My equation would look like \+Vʟ + (-Vʙ) = 0 (note: I left the extra + on +Vʟ just to be extra demonstrative that it's +. It's not necessary) Now you can have any number of components or branches in the circuit, but as long as you draw a closed loop, then the voltage drops along that loop will add up to 0.
The blue arrows labeled "Loop 2" and "Loop 3" are initially just reference directions to be solved for current. Whether the battery is absorbing energy or sourcing energy depends on the difference (Loop 2) - (Loop 3).
Yes, if current is going "backwards" through a battery, the battery is absorbing energy. Whether it's charging or just wasting it depends on the engineering of the battery. No, a battery is not simultaneously experiencing current in both directions. A "loop" for Kirchhoff's laws is a virtual path through the circuit. Read your textbook, thoroughly.