1Yes your answer is correct. But its too late now, I already solved the question [3]
A three end toroid, containing an iron core, is connected into a circuit as shown in the figure. What will the current through switch K be right after closing the switch, if the initial current in the circuit was I0? (The ohmic resistance of the coil is negligible with respect to R.)
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3 Answers
1My answer : - . 8 I 0
Let " I 1 " denote the current flowing through the upper part of the shown circuit and " I 2 " , the current flowing through the lower part . Let " I 3 " denote the current flowing through the switch .
Just before the switch was closed , we had : -
I 1 = I 0 , I 2 = I 0 ;
I 1 + I 2 = 2 I 0
Since , an inductor provides theoretically infinite resistance just after the switch is closed , we still have the sum of these currents unaltered .
The voltage drop across the toroid just after the switch is closed , is : -
V = R I 3 - U
Now we apply Kirchoff ' s Voltage Rule for the whole circuit and the upper part of the circuit respectively .
R I 1 + 2 V = U
R ( I 1 + I 3 ) = V + 2 U
Also applying Kirchoff ' s Junction Rule , we have : -
I 1 = I 2 + I 3
Finally , the total set of available equations is : -
I 1 + I 2 = 2 I 0
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