Moving Charges and Magnetism

If a wire of length ' $L$ ' carrying a current ' $i$ ' is bent in the shape of a semi-circular arc as shown in the figure, then the magnetic field at centre of the arc is

A galvanometer having 30 divisions has a current sensitivity of $0.0625 \frac{d i \nu}{\mu A}$. If it is converted into a voltmeter to read a maximum of 6 V , then the resistance of that voltmeter is

If a current of 15 A passes through a solenoid of length 25 cm , radius 2 cm and number of turns 500 , then the magnetic moment of the solenoid is

Two moving coil galvanometers $A$ and $B$ having identical springs are placed in magnetic fields of 0.25 T and 0.5 T respectively. If the number of turns in $A$ and $B$ are respectively 36 and 48 and the areas of the coils $A$ and $B$ are $...

The maximum magnetic field produced by a current of 12 A passing through a copper wire of diameter 1.2 mm is

If a proton of kinetic energy 8.35 MeV enters a uniform magnetic field of 10 T at right angles to the direction of the field, then the force acting on the proton is
(Mass of proton $=1.67 \times 10^{-27} \mathrm{~kg}$ and Charge of proton $...

The magnetic field at the centre of a long solenoid having 400 turns per unit length and carrying a current ' $i$ ' is $6.24 \times 10^{-2} \mathrm{~T}$. The magnetic field at the centre of another long solenoid having 200 turns per unit le...

Two charged particles of specific charges in the ratio 2:1 and masses in the ratio $1: 4$ moving with same kinetic energy enter a uniform magnetic field at right angles to the direction of the field. The ratio of the radii of the circular p...

If a charged particle enters a uniform magnetic field normally with certain velocity, then the time period of revolution of the particle

A long straight wire of circular cross-section of radius ' $a$ ' is carrying a steady current. The current is distributed uniformly across the cross-section of the wire. The ratio of the magnetic fields at points $0.5 a$ and $1.5 a$ from th...

A solenoid of one metre length and 3.55 cm inner diameter carries a current of 5 A . If the solenoid consists of five closely packed layers each with 700 turns along its length, then the magnetic field at its centre is

The magnetic moment of an electron moving in a circular orbit of radius $R$ with a time period $T$ is

An alpha particle moves along a circular path of radius 0.5 mm in a magnetic field of $2 \times 10^{-2} \mathrm{~T}$. The de-Broglie wavelength associated with the alpha particle is nearly (Planck's constant $=6.63 \times 10^{-34} \mathrm{~...

The force per unit length on a straight wire carrying current of 8 A making an angle of $30^{\circ}$ with a uniform magnetic field of 0.15 T is

The magnetic field at the centre of a current carrying circular coil of radius $R$ is $B_c$ and the magnetic field at a point on its axis at a distance $R$ from its centre is $B_a$. The value of $\frac{B_c}{B_a}$ is

In a wire of radius 1 mm a steady current of 2 A uniformly distributed across the cross-section of the wire is flowing. Then the magnetic field at a point 0.25 mm from the centre of the wire is

If a straight current carrying wire of linear density $0.12 \mathrm{~kg} \mathrm{~m}^{-1}$ is suspended in mid air by a uniform horizontal magnetic field of 0.5 T normal to the length of the wire, then the current through the wire is (Accel...

Two concentric loops $A$ and $B$ of same radius $2 \pi \mathrm{~cm}$ are placed at right angles to each other. If the currents flowing through $A$ and $B$ are 3 A and 4 A respectively, then the net magnetic field at their common centre is

A closely wound solenoid of 1200 turns and area of cross-section $5 \mathrm{~cm}^2$ carries a current. If the magnetic moment of the solenoid is $1.2 \mathrm{JT}^{-1}$, then the current through the solenoid is

A velocity selector is to be constructed to select ions with a velocity of $6 \mathrm{~km} \mathrm{~s}^{-1}$. If the electric field used is $400 \mathrm{~V} \mathrm{~m}^{-1}$, then the magnetic field to be used is

The magnetic field at a distance of 10 cm from a long straight thin wire carrying a current of 4 A is

A charge $q$ is spread uniformly over an isolated ring $R$. The ring is rotated about its natural axis with angular speed $\omega$. The magnetic dipole moment of the ring is

Three rings, each with equal radius $r$ are placed mutually perpendicular to each other and each having centre at the origin of coordinate system. $I$ is current passing through each ring. The magnetic field value at the common centre is

Two toroids with number of turns 400 and 200 have average radii respectively 30 cm and 60 cm . If they carry the same current, the ratio of magnetic fields in these two toroids is

Current flows in a conductor from east to west. The direction of the magnetic field at a point below the conductor is towards

Two infinite length wires carry currents 8 A and $6^{\mathrm{A}}$ respectively and are placed along $X$ and $Y$-axes respectively. Magnetic field at a point $P(0,0, C)$ will

A short magnet oscillates with a time period 0.1 s at a place where horizontal magnetic field is $24 \mu \mathrm{~T}$. A downward current of 18 A is established in a vertical wire kept at a distance of 20 cm east of the magnet. The new time...

When an electron placed in a uniform magnetic field is accelerated from rest through a potential difference $V_1$. It experiences a force $F$. If the potential difference is changed to $V_2$, the force experienced by the electron in same m...

A rectangular loop of sides 25 cm and 10 cm carrying a current of 10 A is placed with its longer side parallel to a long straight conductor 10 cm apart carrying current 25 A . The net force on the loop is

A proton and an alpha particle moving with energies in the ratio $1: 4$ enter a uniform magnetic field of 3 T at right angles to the direction of magnetic field. The ratio of the magnetic forces acting on the proton and the alpha particle ...

A charged particle moving along a straight line path enters a uniform magnetic field of 4 mT at right angles to the direction of the magnetic field. If the specific charge of the charged particle is $8 \times 10^7 \mathrm{C} \mathrm{kg}^{-1...

When two coaxial coils having same current in same direction are brought to each other, then the value of current in both the coils

In hydrogen atom an electron is making $6.6 \times 10^{15} \mathrm{rev} / \mathrm{s}$ around the nucleus of radius $0.47 $$\mathop A\limits^o $. The magnetic field induction produced at the centre of the orbit is nearly.

Two long straight parallel conductors $A$ and $B$ carrying currents 4.5 A and 8 A respectively, are separated by 25 cm in air. The resultant magnetic field at a point which is at a distance of 15 cm from conductor $A$ and 20 cm from conduct...

Two concentric thin circular rings of radii 50 cm and 40 cm , each carry a current of 3.5 A in opposite directions. If the two rings are coplanar, the net magnetic field due to the rings at their centre is

A wire shaped in a regular hexagon of side 2 cm carries a current of 4 A . The magnetic field at the centre of hexagon is

A tightly wound coil of 200 turns and of radius 20 cm carrying current 5 A . Magnetic field at the centre of the coil is

An electron in moving with a velocity $\left[\mathbf{i}+3 \hat{\mathbf{j}} \mathrm{~ms}^{-1}\right.$ in an electric field $(\hat{\mathbf{i}}+6 \hat{\mathbf{j}}+2 \hat{\mathbf{k}}) \mathrm{Vm}^{-1}$ and a magnetic field of $(\Omega \mathbf{j...

A current carrying coil experiences a torque due to a magnetic field. The value of the torque is $80 \%$ of the maximum possible torque. The angle between the magnetic field and the normal to the plane of the coil is

A wire is first bent in the form of a circular coil of 5 turns and the same wire is then bent in the form of another circular coil of 10 turns. If same current is passed in both the coils, then the ratio of the magnetic fields at their cent...

A magnetic field intensity at the centre of a circular wire of radius 0.1 m carrying a current 0.2 A is

The magnetic force $q[\mathbf{v} \times \mathbf{B}]$ is

A particle of mass \(2.2 \times 10^{-30} \mathrm{~kg}\) and charge \(1.6 \times 10^{-19} \mathrm{C}\) is moving at a speed of \(10 \mathrm{~km} \mathrm{~s}^{-1}\) in a circular path of radius 2.8 cm inside a solenoid. The solenoid has $$25 ...

An electron having kinetic energy of 100 eV circulates in a path of radius 10 cm in a magnetic field. The magnitude of magnetic field \(|\mathbf{B}|\) is approximately
[Mass of electron \(=0.5 \mathrm{~MeV} \mathrm{c}^{-2}\), where c is the...

Two infinitely long wires each carrying the same current and pointing in \(+y\) direction are placed in the \(x y\)-plane, at \(x=-2 \mathrm{~cm}\) and \(x=1 \mathrm{~cm}\). An electron is fired with speed \(u\) from the origin making an an...

Two electrons, \(e_1\) and \(e_2\) of mass \(m\) and charge \(q\) are injected into the perpendicular direction of the magnetic field \(B\) such that the kinetic energy of \(e_1\) is double than that of \(e_2\). The relation of their freque...

A toroid has a non ferromagnetic core of inner radius 24 cm and outer radius 25 cm , around which 4900 turns of a wire are wound. If the current in the wire is 12 A , the magnetic field inside the core of the toroid is

What is the net force on the square coil?

A wire of length \(L\) metre carrying a current \(I\) ampere is bent in the form of a circle. Magnitude of its magnetic moment is

Two concentric coils each of radius equal to \(4 \pi ~\mathrm{cm}\) are placed at right angles to each other. If \(10 \mathrm{~A}\) and \(24 \mathrm{~A}\) are the currents flowing through the coils respectively, then the magnetic induction ...