| Directions: In the following questions, a statement of Assertion [A] is followed by a statement of Reason (R). Mark the correct choice as: |
| Assertion [A]: The quantity L/R possesses dimensions of time. |
| Reason (R): To reduce the rate of increases of current through a solenoid should increase the time constant (L/R). |
A) Both Assertion [A] and Reason (R) are true and Reason (R) is the correct explanation of Assertion [A]
B) Both Assertion [A] and Reason (R) are true but Reason (R) is not the correct explanation of Assertion [A]
C) Assertion [A] is true but Reason (R) is false
D) Assertion [A] is false and Reason (R) is also false
Correct Answer: B
Solution :
(b) The relation of induced emf is \[e=\frac{Ldl}{dt}\] and current l is given by \[l=\frac{e}{R}=\frac{1}{R}\cdot \frac{Ldl}{dt}\Rightarrow \frac{dl}{dt}=l\frac{R}{L}=\frac{l}{L/R}\] in order to decreases the rate of increase of current through solenoid. We have to increase the time constant \[\frac{L}{R}\].
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