Magnetic effect of current practice · Mixed difficulty

Similar or same magnetic fields can be
produced by

If we double the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the centre becomes approximately

The current sensitivity of a moving coil galvanometer depends on

A particle of mass $m$, charge $Q$ and kinetic energy is $10 \mathrm{~J}$ enters a transverse uniform magnetic field $\vec{B}$. After 5 seconds the kinetic energy of the particle will be :-

Proton (charge $+\mathrm{e}$, mass $\mathrm{m}$ ) are being accelerated in a cyclotron where a magnetic field $\vec{B}$ is applied perpendicular to the dees and a battery of $V$ volts in connected across the dees to accelerate the protons. The number of revolutions per second (frequency in $\mathrm{Hz}$ ) by the protons is

A current carrying loop of radius $r$ carries a current $I$ in clock wise direction. It is placed in a uniform magnetic field $B$ such that plane of the coil is parallel to field. The net torque on the coil is

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)

Magnetic field dB to a current element at any
point on its axis is

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.

Assertion: The kinetic energy does not change when a particle moves in uniform magnetic field.
Reason: The speed of the particle is not affected by magnetic field.

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 solenoid of 1000 turns per meter has a core with relative permeability 500. Insulated windings of the solenoid carry an electric current of 5A. The magnetic flux density produced by the solenoid is (permeability of free space $= \,\,4\pi \times {10^{ - 7}}\mathrm{H/m}$ )

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

The magnetic field $B$ at a point on one end of a solenoid having $n$ turns per metre length and carrying a current of $i$ ampere is given by