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The electric charge in uniform motion produces :
A man throws balls with the same speed vertically upwards one after the other at an interval of 2 seconds. What should be the speed of the throw so that more than two balls are in the sky at any time? (Given $g=9.8 \text{ m/s}^2$)
A body is released from the top of a tower of height $h$. It takes $t$ sec to reach the ground. Where will be the ball after time $t/2$ sec?
A galvanometer has a coil of resistance $100\Omega$ and gives a full scale deflection for $30 \text{ mA}$ current. If it is to work as a voltmeter of $30\text{ V}$ range, the resistance required to be added will be
When a proton is released from rest in a room, it starts with an initial acceleration $a_0$ towards the east. When it is projected towards the north with a speed $v_0$, it moves with initial acceleration $3a_0$ towards east. The electric and magnetic fields in the room are:
A particle having a mass of $10^{-2}$ kg carries a charge of $5 \times 10^{-8}$ C. The particle is given an initial horizontal velocity of $10^5$ ms$^{-1}$ in the presence of electric field $\vec{E}$ and magnetic field $\vec{B}$. To keep the particle moving in a horizontal direction, it is necessary that: (1) $\vec{B}$ should be perpendicular to the direction of velocity and $\vec{E}$ should be along the direction of velocity. (2) Both $\vec{B}$ and $\vec{E}$ should be along the direction of velocity. (3) Both $\vec{B}$ and $\vec{E}$ are mutually perpendicular and perpendicular to the direction of velocity. (4) $\vec{B}$ should be along the direction of velocity and $\vec{E}$ should be perpendicular to the direction of velocity. Which one of the following pairs of statements are possible?
Two polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_o$ is incident on $P_1$. A third polaroid $P_3$ is kept in between $P_1$ and $P_2$ such that its axis makes an angle $45^\circ$ with that of $P_1$. The intensity of transmitted light through $P_2$ is
For a parallel beam of monochromatic light of wavelength $\lambda$, diffraction is produced by a single slit whose width $a$ is much greater than the wavelength of the light. If $D$ is the distance of the screen from the slit, the width of the central maxima will be:
A particle mass m, charge Q, and kinetic energy T enter a transverse uniform magnetic field of induction $\vec{B}$. After 3 sec the kinetic energy of the particle will be:
A closed-loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR and RO (RQ) are $F_1$, $F_2$ and $F_3$ respectively and are in the plane of the paper and along with the directions shown, the force on the segment QP is
A current-carrying closed loop in the form of a right-angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, the force on the arm AC is:
In order to pass 10% of the main current through a moving coil galvanometer of 99 ohms, the resistance of the required shunt is:
A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I₁ at a distance d from the conductor as shown in figure. The loop will experience
The resistance of an ideal voltmeter is:
The energy equivalent of 0.5 g of a substance is:
A galvanometer having a resistance of $8\ \Omega$ is shunted by a wire of resistance $2\ \Omega$. If the total current is $1\ \text{A}$, the part of it passing through the shunt will be:
If an ammeter A reads 2 A and the voltmeter V reads 20 V, what is the value of resistance R? (Assuming finite resistances of ammeter and voltmeter)
A voltmeter has a range $V$ with a series resistance $R$. With a series resistance $2R$, the range is $V'$. The correct relation between $V$ and $V'$ is:
An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has a magnitude:
A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. Where do the electrons move if the electric field is switched off and the same magnetic field is maintained?