Q. 155.0( 1 Vote )

The figure is a part of a closed circuit. Find the currents i1, i2 and i3


Answer :

IMPORTANT RULE :- WHENEVER THERE ARE CURRENTS COMING FROM DIFFERENT WIRES AND GOING INTO SINGLE ANOTHER DIFFERENT WIRE (THROUGH WHICH THERE IS NO CURRENT COMING) THEN THE CURRENTS ARE ADDED AND IF CURRENT THROUGH ONE WIRE IS GOING INTO TWO DIFFERENT WIRES (WHICH DO NOT HAVE ANY CURRENT RUNNING THROUGH THEM INSTEAD OF THIS CURRENT) THEN THE CURRENT IS DIVIDED IN THEM ACCORDINGLY AND SUBTRACTED FROM THE MAIN COMING CURRENT.

If we know the main current one partition we can find other by using simple maths.


For example- 3A is the main current for forward going 1A and i2 , and 1A and i2 are the partitions of 3A current.


As there is law of conservation of energy.


There is always conservation of current(charge) ,


So 3 = 1 + i2 , by which we can get i2 which is = 3-1 = 2A.


Now to calculate i1 we must obtain the equation of it , which is


i1 + 2 = 3 , i1 = 3-2 = 1A.


Now to calculate i3 we will look at the point where it is getting divided and by whom that is , what is the main current of i3 and the second partition of the main current which is companion with i3,


As i2 = 2A is the main current and it’s one partition is 1.5A and second partition is i3 , so ,


i2 = i3 + 1.5 , 2 = i3 + 1.5 , i3 = 2 - 1.5 = 0.5A


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