The eccentricity of the ellipse $x^2+4y^2+2x+16y+13=0$ is

A capacitor $C$ is first charged fully with potential difference of $V_{0}$ and disconnected from the battery. The charged capacitor is connected across an inductor having inductance $L$. In time $t$, $25 \%$ of the initial energy in the capacitor is transferred to the inductor. The value of $t$ is

Charge $q$ is uniformly distributed over a thin half ring of radius $R$. The electric field at the centre of the ring is

What is the reduction electrode potential (in volts) of a copper electrode when $[Cu^{2+}] = 0.01 \ M$ is in a solution at $25^{\circ} C$? ($E^{\circ}$ of $Cu^{2+}/Cu$ electrode is $+0.34 \ V$)

When glucose reacts with bromine water,the main product is:

When radiation of wavelength $\lambda$ is incident on a metallic surface,the stopping potential is $4.8 \ V$. If the same surface is illuminated with radiation of double the wavelength,then the stopping potential becomes $1.6 \ V$. Then the threshold wavelength for the surface is