question on Electricity

theLEVI

Find the current trough the 5k ohm resistor. how does this change if the 10k ohm resistor is replaced by a 10 ohm resistor ? how does it change if the 2mA current source is replaced by a 2A current source ?


(((((((((((this is the question to the diagram in the attachments ))))))))))))))

the result(given) , apparently is 0.6mA. It does not change in either case, because the voltage across it (and hence its current) is specified by the presence of the two voltage sources which form a loop with it.


Could anyone explain how the result was obtained ? I just have no idea, every time i tried i could not get 0.6 mA... pls help

clartharlear

Kirchhoff's Voltage Law - The algebraic sum of the voltages around a closed loop is zero.
The 5 V, 5k ohm resistor, and the 2 V form a loop, so the voltage dropped across the 5k ohm is 3 V. 3/5k =0.6m A.

The current source and other resistor just don't form part of that closed loop, so changing them won't affect the original loop.

The hard part is identifying the closed loops.

theLEVI

thank you