Magnetic effect of current practice · Medium

Assertion (A): If a proton and an $\alpha$-particle enter a uniform magnetic field perpendicularly with the same speed, then the time period of revolution of the $\alpha$-particle is double than that of proton.
Reason (R): In a magnetic field, the time period of revolution of a charged particle is directly proportional to mass.

Which of the following statements is wrong

A long hollow tube is carrying an electric current along its length distributed uniformly over its surface. The magnetic field

Assertion: A moving charged particle gets energy from magnetic field.
Reason: Magnetic force works on moving charged particle.

An electron is revolving around a proton in a circular path of diameter $0.1 {~nm}$. It produces a magnetic field $14 {~T}$ at a proton. Then the angular speed of the electron is

In the hydrogen atom, the electron is making $6.6 \times 10^{15} \mathrm{rps}$. If the radius of orbits is $0.53 \times 10^{-}$ ${ }^{10} \mathrm{~m}$, then magnetic field produced at the centre of the orbit is

A thin magnetic needle is bent to form a semicircle. What will be the percentage change in equivalent dipole moment?

Ions of different momentum ($p$), having the same charge, enter normally a uniform magnetic field. The radius of the orbit of an ion is proportional to

With the help of potentiometer, we can determine the value of emf of a given cell. The sensitivity of the potentiometer is

(A) Directly proportional to the length of the potentiometer wire

(B) Directly proportional to the potential gradient of the wire

(C) inversely proportional to the potential gradient of the wire

(D) inversely proportional to the length of the potentiometer wire

Choose the correct option for the above statements:

A magnetic field of $\left(4.0 \times 10^{-3} \vec{k}\right) \mathrm{T}$ exerts a force of $(4.0 \vec{i}+3.0 \vec{j}) \times 10^{-10} \mathrm{~N}$ on a particle having a charge of $1.0 \times 10^{-9} \mathrm{C}$ and going in the $x-y$ plane. Find the velocity of the particle.

Assertion: Resistance of an ammeter is less than the resistance of a milli ammeter.

Reason: Value of shunt required in case of ammeter is more than a milli ammeter.

Two parallel wires carrying currents in
opposite directions

A magnetic field exerts no force on

Assertion: Cyclotron is a accelerating device.
Reason: Neutrons can be accelerated by the cyclotron.

A charged particle moving in a magnetic field
experiences a resultant force

A cyclotron is used to accelerate protons. If the operating magnetic field is $1.0 \mathrm{~T}$ and the radius of the cyclotron 'dees' is $60 \mathrm{~cm}$, the kinetic energy of the accelerated protons in $\mathrm{MeV}$ will be

$\left[\right.$ Use $m_p=1.6 \times 10^{-27} \mathrm{~kg}, e=1.6 \times 10^{-19} \mathrm{C}$ ]

A proton, a deuteron and $\alpha$ particle accelerated through the same potential difference enter the region of uniform magnetic field, moving at right angles to magnetic field. The ratio of their kinetic energies will be

A positive charged particle $q$, mass $m$ is dropped from certain point above ground. A constant horizontal magnetic field of magnitude $B$ is present. If charge falls down by height $h$, then speed of charge is (neglect effect of air)

In a region an electron is moving in a circle. What can be the possible field there?

The maximum current that can be measured by a galvanometer of resistance $\mathrm{40}\,\,\mathrm{\Omega }$ is $\mathrm{10}\,\,\mathrm{mA}$. It is converted into a voltmeter that can read upto $\mathrm{50}\,\,\mathrm{V}$. The resistance to be connected is series with the galvanometer (in ohm) is

Two galvanometers 'A' and 'B' require currents of $4 \mathrm{~mA}$ and $7 \mathrm{~mA}$, respectively to produce the same deflection of 20 divisions. If ' $\mathrm{S}_{\mathrm{A}}$ ' and ' $\mathrm{S}_{\mathrm{B}}$ ' are their sensitivities, respectively, then

Assertion: Cyclotron is used to accelerate heavy charged particles, such as proton. It not suitable for accelerating light charged particles, such as electrons.

Reason: Specific charge of proton is more as compared to electron.

Two wires are held perpendicular to the plane of paper and are $5 \mathrm{~m}$ apart. They carry currents of $2.5 \mathrm{~A}$ and $5 \mathrm{~A}$ in same direction. Then, the magnetic field strength $(B)$ at a point midway between the wires will be

Assertion: A circular loop carrying current lies in XY plane with its centre at origin having a magnetic flux in negative Z-axis.

Reason: Magnetic flux direction is independent of the direction of current in the conductor.

A particle moving in a circle of radius $R$ with a uniform speed takes a time $T$ to complete one revolution. If this particle were projected with the same speed at an angle '$\theta$' to the horizontal, the maximum height attained by it equals $4R.$ The angle of projection '$\theta$' is then given by:

Sensitivity of potentiometer can be increased by

Assertion: If the current in a solenoid is
reversed in direction while keeping the same
magnitude, the magnetic field energy stored in the
solenoid decreases.
Reason: Magnetic field energy density is
proportional to square of current

A straight conductor carries a current of $5 \mathrm{~A}$. An electron travelling with a speed of $5 \times 10^6$ $\mathrm{ms}^{-1}$ parallel to the wire at a distance of $0.1 \mathrm{~m}$ from the conductor, experiences a force of

The magnetic field applied on a cyclotron is $3.5 {~T}$. What will be the frequency of electric field that must be applied between the Dee's in order to accelerate a proton?

A proton is moving in a uniform magnetic field $B$ in a circular path of radius a in a direction perpendicular to z-axis along which field $B$ exists. Calculate the angular momentum. If the radius is a charge on proton is $e$.