Physics Test - ...

The capacitance of a parallel plate capacitor with air as medium is 3 $\mathrm{\mu }\mathrm{F}$. With the introduction of a dielectric medium between the plates, the capacitance becomes 15 $\mathrm{\mu }\mathrm{F}$. The permittivity of the medium is

The half-life period of radium is $1600 \mathrm{y}\mathrm{r}.$ The fraction of a sample of radium that would remain after $6400 \mathrm{y}\mathrm{r}$ is

A hollow charged metal sphere has radius r. If the potential difference between its surface and a point at a distance \(3 \mathrm{r}\) from the centre is \(\mathrm{V}\)

then the electric field intensity at distance \(3 \mathrm{r}\) from the centre is -

The resistance of a wire is R ohm. If it is melted and stretched to n times its orginal length, its new resistance will be

An unknown resistance R₁ is connected in series with a resistance of 10 $\mathrm{\Omega }$. This combination is connected to one gap of meter bridge while a resistance R₂ is connected in the other gap. The balance point is at 50 cm, Now, when the 10 $\mathrm{\Omega }$ resistance is removed the balance point shifts to 40 cm. The value of R₁ (in ohm) is

A capacitor has capacitance C and reactance X if capacitance and frequency become double, then reactance will be

In a Young’s double slit experiment, the distance between the two identical slits is 6.1 times larger than the slit width. Then the number of interference maxima observed within the central maximum of the single slit diffraction pattern is :

Electromagnetic waves travel in a medium with a speed of 2 × 10⁸  m s⁻¹.The relative permeability of the medium is 1. Find the relative permittivity.

An $\mathrm{\alpha }$ particle of mass m is in equilibrium in vertically upward electric field E. The charge on a particle is

Half life of a radioactive element is 3 months. What will be the fraction of that element leftover after one year?