When two coaxial coils having same current in same direction are brought to each other, then the value of current in both the coils

A resistance of $20 \Omega$ is connected to a source of an alternating potential $V=200 \sin (10 \pi t)$. If $t$ is the time taken by the current to change from the peak value to rms value, then $t$ is (in seconds)

The average value of electric energy density in an electromagnetic wave is where $E_0$ is peak value

An electron of mass $m$ with initial velocity $\mathbf{v}=v_0 \hat{\mathbf{i}}\left(v_0>0\right)$ enters in an electric field $\mathbf{E}=-E_0 \hat{\mathbf{i}}$ ( $E_0$ is constant $>0$ ) at $t=0$. If $\lambda$ is its de-Broglie wavelength initially, then the de-Broglie wavelength after time $t$ is