Ruma reached the metro station and found that the escalator was not working. She walked up the stationary escalator with velocity $v_1$ in time $t_1$. On other day if she remains stationary on the escalator moving with velocity $v_2$, then escalator takes her up in time $t_2$. The time taken by her to walk up with velocity $v_1$ on the moving escalator will be
A quantity $X$ is given by $\varepsilon_0 L \frac{\Delta V}{\Delta t}$, where $\varepsilon_0$ is the permittivity of free space, $L$ is the length, $\Delta V$ is a potential difference and $\Delta t$ is a time interval. The dimension of $X$ is same as that of
A diode is connected in parallel with a resistance as shown in Figure. The most probable current (I) - voltage (V) characteristic is




The minimum wavelength of Lyman series lines is $P$, then the maximum wavelength of these lines is