Magnetic effect of current practice · Medium

A conducting rod of $1 \mathrm{~m}$ length and $1 \mathrm{~kg}$ mass is suspended by two vertical wires through its ends. An external magnetic field of $2 \mathrm{~T}$ is applied normal to the rod. Now the current to be passed through the rod so as to make the tension in the wires zero is [Take $g=10 {~ m s}^{-2}$ ]

A solenoid having area $A$ and length $l$ is filled with a material having relative permeability 2. The magnetic energy stored in the solenoid is:

Current $i$ is flowing in a coil of area $A$ and number of turns $N$, then magnetic moment of the coil, $M$ is equal to

Assertion: Magnetic moment of toroid is zero.
Reason: Magnetic field outside the volume of current carrying toroid is zero.

A force $\vec{F}$, acting on an electric charge $q$, in presence of an electromagnetic field, moves the charge parallel to the magnetic field with velocity $\vec{v}$. Then $\vec{F}$ is equal to (where $\vec{E}$ and $\vec{B}$ are electric field and magnetic field respectively)

Two similar moments $P$ and $Q$ each magnetic moment $M$ are taken. If $P$ is cut alor its axial line and $Q$ is cut along its equator line all the four pieces obtained have each of

If the current in the toroidal solenoid increase uniformly from zero to $6.0 \mathrm{~A}$ in $3.0 \mu \mathrm{s}$. Self inductance of the toroidal solenoid is $40 \mu \mathrm{H}$. The magnitude of self induced emf is

When a high resistance R is connected in series with a voltmeter of resistance G, the range of the voltmeter increases 10 times then G:R will be

A uniform magnetic field $B$ and electric field $E$ exist along $y$ and negative $z$ axis respectively. Under the influence of these fields a charge particle moves along $O A$ undeflected. If electric field is swithed off, find the pitch of helical trajectory in which the particle will move.

A wire of length L is placed parallel to the lines
of force in a uniform magnetic field B. If I is
the current in the wire, then it will experience:

Assertion (A): If a proton and an $\alpha$-particle enter a uniform magnetic field perpendicularly, with the same speed, the time period of revolution of $\alpha$-particle is double that of proton.

Reason (R): In a magnetic field, the time period of revolution of a charged particle is inversely proportional its specific charge.

A narrow vertical rectangular coil is suspended from the middle of its upper side with its plane parallel to a uniform horizontal magnetic field of $0.02 \mathrm{~T}$. The coil has 10 turns and the lengths of its vertical and horizontal sides are $0.1\,m$ and $0.05\,m$ respectively. Calculate the torque on the coil when a current of $5 \mathrm{~A}$ is passed into it. What would be the new value of the torque if the plane of the vertical coil was initially at $60^{\circ}$ to the magnetic field and a current of $5 \mathrm{~A}$ was passed into the coil.

The law which states that ‘a variation in an
electric field causes magnetic field, is

Find the current density as a function of distance $r$ from the axis of a radially symmetrical parallel stream of electrons if the magnetic induction inside the stream varies as $B=b r^2$, where $b$ and $a$ are positive constants.

A current of $10 \mathrm{~A}$ is flowing east to west in a long wire kept horizontally in the east-west direction. Find magnetic field in a horizontal plane at a distance of (i) $10 \mathrm{~cm}$ north (ii) $20 \mathrm{~cm}$ south from the wire

Field inside a solenoid is

The magnetic moment is NOT associated with

The magnetic induction at a point near end of a current carrying solenoid is $(I=$ current, $\mathbf{n}=$ number of turns per unit length, $\mu_0=$ permeability

Assertion (A) : Power of a magnetic force on a charged particle is always zero.

Reason (R) : Power of electric force on charged particle cannot be zero.

A small conducting circular loop is placed inside a long solenoid carrying a current. The plane of the loop contains the axis of the solenoid. If the current in the solenoid is varied, the current induced in the loop is

An electron enters a magnetic field along perpendicular direction. Following quantity will remain constant

The electric current in a circular coil of four turns produces a magnetic induction $32 \mathrm{~T}$ at its centre. The coil is unwound and is rewound into a circular coil of single turn, the magnetic induction at the centre of the coil by the same current will be

When $\sqrt 3 \;ampere$ current is passed in a tangent galvanometer, there is a deflection of $30^\circ$ in it. The deflection obtained when $3\;amperes$ current is passed, is

At the mid-point along the length of a long solenoid, the magnetic field is equal to $X$. If the length of the solenoid is doubled and the current is reduced to half the field at the new mid-point will be nearest to

An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii ${r_e},{r_p},{r_\alpha }$ respectively, in a uniform magnetic field B. the relation between ${r_e},{r_p},{r_\alpha }$ is

If a shunt of $15\,\,\Omega$ is connected with a galvanometer of resistance $60\,\,\Omega$, then the resistance necessary to be connected in series with circuit for keeping the main current constant.

An electrically charged particle enters into a uniform magnetic induction field in a direction perpendicular to the field with a velocity $\mathrm{v}.$ Then, it travels

Assertion (A) : An electron and a proton are accelerated by same potential difference and then enter in uniform transverse magnetic field. The radii of the two will be different.

Reason (R) : Charges on them are different.

Assertion: Cyclotron does not accelerate electron.

Reason: Mass of the electron is very small.

A circular coil of 200 turns has a radius of $10 \mathrm{~cm}$ and carries a current of $2.0 \mathrm{~A}$. (a) Find the magnitude of the magnetic field $\vec{B}$ at the centre of the coil. (b) At what distance from the centre along the axis of the coil will the field $B$ drop to half its value at the centre? $(\sqrt[3]{4}=1.5874 \ldots)$