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Alternating Current — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsAlternating Current1 Mark
MCQ
For two statements are given-one labelled Assertion $(A)$ and the other labelled Reason $(R)$. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: A bulb connected in series with a solenoid is connected to $A.C.$ source. If a soft iron core is introduced in the solenoid, the bulb will glow brighter.
Reason: On introducing soft iron core in the solenoid, the inductance decreases.
  • A
    Both $A$ and $R$ are true and $R$ is the correct explanation of $A$.
  • B
    Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
  • C
    $A$ is true but $R$ is false.
  • ✓
    $A $ is false and $R$ is also false.
✓

Answer

Correct option: D.
$A $ is false and $R$ is also false.
On introducing soft iron core, the bulb will glow dimmer.
This is because on introducing soft iron core in the solenoid, its inductance $L$ increases, the inductive reactance, $X_L= W_L$ increases and hence the current through the bulb decreases.

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