The capacitance of an air-filled parallel-plate capacitor is 60 pF. When a dielectric slab whose thickness is half the distance between the plates, is placed on one of the plates covering it entirely, the capacitance becomes 86 pF. Neglecting the fringing effects, the relative permittivity of the dielectric is _____________ (up to 2 decimal places).

Four power semiconductor devices are shown in the figure along with their relevant terminals. The device(s) that can carry dc current continuously in the direction shown when gated appropriately is (are)

The waveform of the current drawn by a semi-converter from a sinusoidal AC voltage source is shown in the figure. If I₀ = 20 A, the rms value of fundamental component of the current is ___________A (up to 2 decimal places).

A phase controlled single phase rectifier, supplied by an AC source, feeds power to an R-L-E load as shown in the figure. The rectifier output voltage has an average value given by $${V_0} = {{{V_m}} \over {2\pi }}\left( {3 + \cos \alpha } \right)$$, where $${V_m} = 80\pi $$ volts and $$\alpha $$ is the firing angle. If the power delivered to the lossless battery is 1600 W, $$\alpha $$ in degree is________ (up to 2 decimal places).