Assertion : `L//R and CR` both have same dimensions.
`L//R and CR` both have divisions on circular scale.

Options

A. If both the assertion and reason are true and reason is correct explanation of the assertion .
B. If both the assertion and reason are true but reason is not a correct explanation of the assertion .
C. If the assertion is true but the reason is false.
D. If both assertion and reason are false.

Answer

C

Explanation

Induced e.m.f. `(epsi)=(Ldi)/(dt)` and current ` (i)=(epsi)/(R) =(1)/(R) xx (Ldi)/(dt)` or `(L)/(R)=(idt)/(di)=("current" xx "time")/("current")=`time .
In order to increase the rate of increase of current through a solenoid , we increase the time constant (L/R). Since L of the given solenoid is constant , therefore we use a high resistance in series with it .