A square wire loop of $10.0\,\text{cm}$ side lies at right angles to a uniform magnetic field of $20\,\text{T}$. A $10\,\text{V}$ light bulb is in series with the loop as shown in the figure. The magnetic field is decreasing steadily to zero over a time interval $\Delta t$. The bulb will shine with full brightness if $\Delta t$ is equal to