Moving Charges And Magnetism - Electromagnetism - Physics Previous Year Questions

A horizontal overhead power line carries a current of 90 A in East to West direction. What is the magnitude and direction of the magnetic field due to the current, 1.5 m below the line?

An electron moves with speed of 2 \(\times\) 10\(^5\) m/s along the positive x-direction in a magnetic field \(B = (\widehat i - 4\widehat j - 3\widehat k)\,T\). The magnitude of the force (in N) experienced by the electron is

A moving coil galvanometer has 28 turns and area of coil is \(4\times 10^{-2}\) m\(^2\). If the magnetic field is 0.2 T, then to increase the sensitivity by 25% without changing area and field, the number of turns should be changed to

The particle that cannot be accelerated by a cyclotron is

A long solenoid has 20 turns cm\(^{-1}\). The current necessary to produce a magnetic field of 20 mT inside the solenoid is approximately

Two particles of masses \(m_1=m,m_2=2m\) and charges \(q_1=q,q_2=2q\) entered into uniform magnetic field. Find \(F_1/F_2\) (force ratio).

A constant current flows from A to B as shown in the figure. What is the direction of current in the circle?

A regular hexagon of side \(m\) which is a wire of length 24 m is coiled on that hexagon. If current in hexagon is \(I\), then the magnetic moment,

An electric current $I$ enters and leaves a uniform circular wire of radius $r$ through diametrically opposite points. A charged particle \(q\) moves along the axis of circular wire passes through its centre with speed \(v\). The magnetic force on the particle when it passes through the centre has a magnitude

A magnetic field does not interact with:

A metallic rod of \(10 \mathrm{~cm}\) is rotated with a frequency 100 revolution per second about an axis perpendicular to its length and passing through its one end in uniform transverse magnetic field of strength \(1 \mathrm{~T}\). The emf developed across its ends is:

The radius of the current carrying circular coil is doubled keeping the current passing through it the same. Then the ratio of the magnetic field produced at the centre of the coil before the doubling of the radius to the magnetic field after doubling of the radius.

A circular loop of area \(0.04 \mathrm{~m}^2\) carrying a current of \(10 \mathrm{~A}\) is held with its plane perpendicular to a magnetic field induction \(0.4 \mathrm{~T}\) Then the torque acting on the circular loop is :

A long horizontal wire \(\mathrm{P}\) carries current of \(50 \mathrm{~A}\) from left to right. It is rigidly fixed. Another fine wire \(\mathrm{Q}\) is placed directly above and parallel to \(\mathrm{P}\). The mass of the wire is '\(\mathrm{m}\)' \(\mathrm{kg}\) and carries a current of '\(\mathrm{I}\)' A. The direction of current in \(\mathrm{Q}\) and position of wire \(\mathrm{Q}\) from \(\mathrm{P}\) so that the wire \(\mathrm{Q}\) remains suspended are

A charge of \(+1 \mathrm{C}\) is moving with velocity \(\vec{V}=(2 \mathrm{i}+2 \mathrm{j}-\mathrm{k}) \mathrm{ms}^{-1}\) through a region in which electric field \(\vec{E}=(\mathrm{i}+\mathrm{j}-3 \mathrm{k}) \quad \mathrm{NC}^{-1}\) and magnetic field \(\vec{B}=(\mathrm{i}-2 \mathrm{j}+3 \mathrm{k}) \mathrm{T}\) are present. The force experienced by the charge is

To increase the current sensitivity of a moving coil galvanometer by \(25 \%\), its resistance is increased so that the new resistance becomes twice its initial resistance. By what factor does the voltage sensitivity change?

A wire of length \(2 \mathrm{~m}\) carries a current of \(1 \mathrm{~A}\) along the \(\mathrm{x}\) axis. A magnetic field \(B=B_0(i+j+k)\) tesla exists in space. The magnitude of magnetic force on the wire is

A negative charge particle is moving upward in a magnetic field which is towards north. The particle is deflected towards

A current I flows in an infinitely long wire with cross section in the form of semi-circular ring of radius \(1 \mathrm{~m}\). The magnitude of the magnetic induction along its axis is

Two circular coils of radius '\(a\)' and '\(2 a\)' are placed coaxially at a distance ' \(x\) and '\(2 x\)' respectively from the origin along the \(\mathrm{X}\)-axis. If their planes are parallel to each other and perpendicular to the \(\mathrm{X}\) - axis and both carry the same current in the same direction, then the ratio of the magnetic field induction at the origin due to the smaller coil to that of the bigger one is: