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7.Alternating Current
medium
In figure, the switch $S$ is closed so that a current flows in the iron-core inductor which has inductance $L$ and the resistance $R$. When the switch is opened, $a$ spark is obtained in it at the contacts. The spark is due to
A
$a$ slow flux change in $L$
B
$a$ sudden increase in the emf of the battery $B$
C
$a$ rapid flux change in $L$
D
$a$ rapid flux change in $R$
Solution
When switch $S$ is closed, we see that the current flows through the circuit and there will be energy stored in the inductor. When switch $S$ is opened, the voltage drop across the resistance will instantly come to zero, but in the inductor, there will be some energy and due to that a rapid flux change occurs in $L$.
$\because \phi= LI$
Standard 12
Physics
