| Assertion (A): The dimension of L/R is time. |
| Reason (R): Time constant (UR) should be increased to reduce the rate of increase of current through a solenoid. |
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
D) A is false and R is true
Correct Answer: B
Solution :
| Option [b] is correct. |
| Explanation: For a solenoid, the magnitude of induced emf |
| \[e=L\frac{di}{dt}\] |
| \[i=\frac{e}{R}=\left( \frac{L}{R} \right)\left( \frac{di}{dt} \right)\] |
| \[\frac{di}{dt}=\frac{i}{\frac{L}{R}}\] |
| In left hand side of the above equation, denominator is time. So, in right hand side, the denominator should be time. So, dimension of L/R is time. |
| So, the assertion is true. |
| If L/R increases, di/dt decreases. |
| So, reason is also true. |
| But reason cannot properly explain the assertion. |
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