In the circuit shown below, the key is pressed at time t = 0. Which of the following statement(s) is (are) true?

An incandescent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evaporation of tungsten from the filament. If the bulb is powered at constant voltage, which of the following statement(s) is (are) true?

A parallel plate capacitor having plates of area S and plate separation d, has capacitance C₁ in air. When two dielectrics of different relative permittivities ($$\varepsilon $$₁ = 2 and $$\varepsilon $$₂ = 4) are introduced between the two plates as shown in the figure, the capacitance becomes C₂. The ratio $${{{C_2}} \over {{C_1}}}$$ is

In an aluminium (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure. The electrical resistivities of Al and Fe are 2.7 $$\times$$ 10^$$-$$8$$\Omega$$ m and 1.0 $$\times$$ 10^$$-$$7 $$\Omega$$ m, respectively. The electrical resistance between the two faces P and Q of the composite bar is