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When a block of mass M is suspended by a long wire of length L, the length of the wire becomes (L + l). The elastic potential energy stored in the extended wire is :
The simple Bohr model is not applicable to He-4 atom because: (a) He-4 is an inert gas. (b) He-4 has neutrons in the nucleus. (c) He-4 has one more electron. (d) electrons are not subject to central forces. Choose the correct option:
A straight conductor carrying current $I$ splits into two parts as shown in the figure. The radius of the circular loop is $R$. The total magnetic field at the centre $P$ of the loop is:
A vertical spring with a force constant $k$ is fixed on a table. A ball of mass $m$ at a height $h$ above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance $d$. The net work done in the process is:
A current loop in a magnetic field:
In an ideal transformer, the turns ratio is $N_p/N_s = 1/2$. The ratio $V_s:V_p$ is equal to (the symbols carry their usual meaning):
Two toroids 1 and 2 have total no. of turns 200 and 100 respectively with average radii 40 cm and 20 cm respectively. If they carry the same current i, what will be the ratio of the magnetic fields along the two loops?
$4.0 \text{ gm}$ of gas occupies $22.4 \text{ litres}$ at NTP. The specific heat capacity of the gas at a constant volume is $5.0 \text{ J K}^{-1}\text{mol}^{-1}$. If the speed of sound in the gas at NTP is $952 \text{ ms}^{-1}$, then the molar heat capacity at constant pressure will be: ($R=8.31 \text{ J K}^{-1}\text{mol}^{-1}$)
A wire carrying current $I$ has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to the X-axis while the semicircular portion of radius $R$ is lying in the Y-Z plane. The magnetic field at point $O$ is:
A uniform conducting wire of length $12a$ and resistance $R$ is wound up as a current-carrying coil in the shape of: (i) an equilateral triangle of side $a$ (ii) a square of side $a$ The magnetic dipole moments of the coil in each case respectively are:
A long straight wire of radius $a$ carries a steady current $I$. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields $B$ and $B'$ at radial distances $a/2$ and $2a$ respectively, from the axis of the wire, is:
A mass $m$ moves in a circle on a smooth horizontal plane with velocity $v_0$ at a radius $R_0$. The mass is attached to a string that passes through a smooth hole in the plane, as shown in the figure. The tension in the string is increased gradually and finally, $m$ moves in a circle of radius $\frac{R_0}{2}$. The final value of the kinetic energy is:
A thick current-carrying cable of radius 'R' carries current 'I' uniformly distributed across its cross-section. The variation of magnetic field B(r) due to the cable with the distance 'r' from the axis of the cable is represented by:
The angle between the electric lines of force and the equipotential surface is
Two identical long conducting wires $AOB$ and $COD$ are placed at right angle to each other, with one above other such that $O$ is their common point for the two. The wires carry $I_1$ and $I_2$ currents, respectively. Point $P$ is lying at distance $d$ from $O$ along a direction perpendicular to the plane containing the wires. The magnetic field at the point $P$ will be:
When a uranium isotope $_{92}^{235}\mathrm{U}$ is bombarded with a neutron, it generates $_{36}^{89}\mathrm{Kr}$, three neutrons and:
An infinitely long straight conductor carries a current of $5 \text{ A}$. An electron is moving with a speed of $10^5 \text{ m/s}$ parallel to the conductor. The perpendicular distance between the electron and the conductor is $20 \text{ cm}$ at an instant. Calculate the magnitude of the force experienced by the electron at that instant.
A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the centre of the coil is: (Take permeability of free space as $4\pi \times 10^{-7}$ SI units)
A circuit contains an ammeter, a battery of $30\text{ V}$ and a resistance $40.8\,\Omega$ all connected in series. If the ammeter has a coil of resistance $480\,\Omega$ and a shunt of $20\,\Omega$ then reading in the ammeter will be :
A small mass attached to a string rotates on a frictionless table top as shown. If the tension on the string is increased by pulling the string causing the radius of the circular motion to decrease by a factor of $2$, the kinetic energy of the mass will: