Q. A radioactive substance decays to $1/{16}^{th}$ of its initial mass in $40$ days. The half life of the substance, in days, is?

1. $20$
2. $10$
3. $5$
4. $2.5$

Q. The electrostatic potential energy of two point charges, $1$ $\mu$C each, placed $1$ meter apart in air is?

1. $9\times {10}^3$J
2. $9\times {10}^9$J
3. $9\times {10}^{-3}$J
4. $9\times {10}^{-3}$eV

Q. An a.c. generator generates an emf '$\epsilon$' where $\epsilon =314\sin \left(50\pi t\right)$volt. Calculate the frequency of the emf $\epsilon$.

Q. A wire of resistance 'R' is cut into 'n' equal parts. These parts are then connected in parallel with each other. The equivalent resistance of the combination is?

1. nR
2. $R/n^2$
3. $n/R^2$
4. $R/n$

Q. Three capacitors $C_1=3\mu F$, $C_2=6\mu F$ and $C_3=10\mu F$ are connected to a $50$V battery as shown in the figure.
Calculate:
(i) The equivalent capacitance of the circuit between points A and B.
(ii) The charge on $C_1$.

Q. In a meter bridge circuit, resistance in the left hand gap is $2\Omega$ and an unknown resistance X is in the right hand gap as shown in Figure. The null point is found to be $40$cm from the left end of the wire. What resistance should be connected to X so that the new null point is $50$cm from the left end of the wire?

Q. On which conservation principle is Kirchoff's Second Law of electrical networks based?

Q. Magnetic susceptibility of platinum is $0.0001$. Its relative permeability is?

1. $1.0000$
2. $1.0001$
3. $0.9999$
4. $0$

Q. When a light wave travels from air to glass.

1. Its wavelength decreases
2. Its frequency decreases
3. There is no change in wavelength
4. Its wavelength increases

Q. Calculate the momentum of a photo of energy $6\times {10}^{-19}$J.

Q. PQ is a long straight conductor carrying a current of $3$A as shown in Figure. An electron moves with a velocity of $2\times {10}^{7}m{s}^{-1}$ parallel to it. Find the force acting on the electron.

Q. Using Ampere's circuital law, obtain an expression for the magnetic flux density 'B' at a point 'X' at a perpendicular distance 'r' from a long current carrying conductor.(Statement of the law is not required).

Q. How is fringe width of an interference pattern in Young's double slit experiment affected if the two slits are brought closer to each other?

Q. Calculate magnetic flux density of the magnetic field at the centre of a circular coil of $50$ tunrs, having radius of $0.5$m and carrying a current of $5$A.

Q. What is the minimum energy which a gamma ray photon must possess in order to produce electron-positron pair?

Q. Show that electric potential at a point P, at a distance 'r' from a fixed point charge Q, is given by $V=\left(\frac{1}{4\pi {ϵ}_0}\right)\frac{Q}{r}$.

Q. How can the spherical aberration produced by a lens be minimised?

Q. Why nuclear fusion reaction is also called thermo-nuclear reaction?

Q. The horizontal component of earth's magnetic field at a place is $\frac{1}{\sqrt{3}}$ times the vertical component. Determine the angle of dip at that place.

Q. According to Bohr, 'Angular momentum of an orbiting electron is quantised'. What is meant by this statement?

Q. A moving coil galvanometer has a coil of resistance $59\Omega$. It shows a full scale deflection for a current of $50$mA. How will you convert it to an ammeter having a range of $0$ to $3$A?

Q. What is meant by drift speed of free electrons?

Q. In a regular prism, what is the relation between angle of incidence and angle of emergence when it is in the minimum deviation position?

Q. A converging lens of focal length $40$cm is kept in contact with a diverging lens of focal length $30$cm. Find the focal length of the combination.

Q. Two resistors $R_1=60\Omega$ and $R_2=90\Omega$ are connected in parallel. If electric power consumed by the resistor $R_1$ is $15$W, calculate the power consumed by the resistor $R_2$.

Q. Maximum torque acting on an electric dipole of moment $3\times {10}^{-29}$Cm in a uniform electric field E is $6\times {10}^{-25}$Nm. Find E.

Q. Figure shows two resistors $R_1$ and $R_2$ connected to a battery having an emf of $40$V and negligible internal resistance. A voltmeter having a resistance of $300\Omega$ is used to measure potential difference across $R_1$. Find the reading of the voltmeter?

Q. Intensity of electric field at a perpendicular distance of $0.5$m from an infinitely long line charge having linear charge density $\left(\lambda \right)$ is $3.6\times {10}^{3}V{m}^{-1}$. Find the value of $\lambda$.

Q. With what type of source of light are cylindrical wave fronts associated?

Q. Show the variation of voltage with time, for a digital signal.