List of top Physics Questions

A system consists of a uniformly charged sphere of radius $R$ and a surrounding medium filled by a charge with the volume density $\rho=\frac{\alpha}{r}$, where $\alpha$ is a positive constant and $r$ is the distance from the centre of the sphere. Find the charge of the sphere for which the electric field intensity $E$ outside the sphere is independent of $R$.
A straight vertical conductor carries a current. At a point 5 cm due north of it, the magnetic induction is found to be $20\,\mu T$ due east. The magnetic induction at a point 10 cm east of it will be
A square loop of side L carries a current I. Another smaller square loop of side l [ l < < L ) carrying a current i is placed inside the bigger loop such that they are coplanar with their centres coinciding. If the currents in the loops are in the same direction the magnitude of the torque on the smaller loop is
A square loop of side 22cm is changed to a circle in time 0.4 sec with its plane normal to a inagnetic field 0.2T. The emf induced is
A solid sphere of mass $1 \,kg$ and radius $1 \,m$ rolls without slipping on a fixed inclined plane with an angle of inclination $\theta=30^{\circ}$ from the horizontal Two forces of magnitude $1 \,N$ each, parallel to the incline, act on the sphere, both at distance $r=05 \,m$ from the center of the sphere, as shown in the figure The acceleration of the sphere down the plane is ____ $ms ^{-2}$ (Take $g=10 \,m s ^{-2}$)
A long solenoid is formed by winding 70 turns cm-1. If 2.0 A current flows, then the magnetic field produced inside the solenoid is _________ (µ0 = 4π × 10-7 TmA-1)
A rigid spherical body is spinning around an axis without any external torque. Due to rise of temperature its volume increases by 3% . Then percentage change in its angular speed is
In the Bohr model of the hydrogen atom, let R, V and E represent the radius of the orbit, speed of the electron and total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n ?
A plane progressive wave cannot be represented by
A person can swim in still water at 5 m/s. He moves In a river of velocity 3 m/s, first down the stream and next same distance up the stream. The ratio of times taken are.
A square wire of each side l carries a current I. The magnetic field at the mid point of the square is

A pair of stationary and infinitely long bent wires are placed in the x-y plane as shown in figure. The wires carry currents of 10A each as shown. The segments L and M are along the x-axis. The segments P and Q are parallel to the y-axis such that OS = OR = 0.02m. Find magnitude and direction of the magnetic induction at the origin O.
A pair of stationary and infinitely long bent wires are placed in the x-y plane as shown in figure

A number of bullets are fired horizontally with different velocities from the top of a tower they reach the ground
A mild steel wire of length 2L and cross-sectional area A is stretched, well within elastic limit, horizontally between two pillars as shown in the figure. A mass M is suspended from the mid-point of the wire. Strain in the wire is
A liquid drop of diameter D breaks up into 27 drops. Find the resultant change in energy
A force of $- F \hat{k}$ acts on $O$, the origin of the coordinate system. The torque about the point $(1,-1)$ is
A convex lens forms a real image of the object when the lens is at a distance of 1 m form the object. The size of the image is 3 times that of the object. The position of the object and the screen are kept fixed but the distance of lens from the object is doubled. The image is now one half of the size of the object, the focal length of the lens is
A blacksmith fixes iron ring on the rim of the wooden wheel of bullock cart . the diameter of the rim and the iron ring are 5.243 m and 5.231 m respectively at $27^{\circ} C$ . The temperature should the ring be heated so as to fit the rim of the wheel?
A body is placed on rough $\left(\mu=\frac{1}{3\sqrt{3}}\right)$ inclined plane. $A$ force $F$ is needed to stop this body to slide downward. $A$ force $2F$ is needed so that the body is just about to move upwards. Slope of inclined plane is
A charged particle q is placed at the centre O of cube of length L (A B C D E F G H). Another same charge q is placed at a distance L from O. Then the electric flux through ABCD is
A point dipole with dipole moment, $\vec{p} = p_0 \hat{k}$ , is kept at the origin. An external electric field given by, $\vec{E} = E_0 ( 2\hat{i} - 3\hat{j} + 4\hat{k})$ , is applied on it. Which one of the following statements is true ?
The coefficient of linear expansion of a metal rod is $12 \times 10^{-6} / ^{\circ}C$ , its value in per its value in per $^{\circ}F$
Answer the following : 
  1. You are given a thread and a metre scale. How will you estimate the diameter of the thread ? 
  2. A screw gauge has a pitch of 1.0 mm and 200 divisions on the circular scale. Do you think it is possible to increase the accuracy of the screw gauge arbitrarily by increasing the number of divisions on the circular scale ? 
  3. The mean diameter of a thin brass rod is to be measured by vernier calipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only ?
The half-life of thorium X is 3.64 days. After how many days will 0.1 of the mass of a sample of the substance remain undecayed?
Figure 2.11shows the x-t plot of one dimensional motion of a particle. Is it correct to say from the graph that the particle moves in a straight line for t < 0 and on a parabolic path for t >0 ? If not, suggest a suitable physical context for this graph.
x-t plot of one dimensional motion of a particle
Figure 2.11