Moving Charges and Magnetism · Physics · KCET
MCQ (Single Correct Answer)
A moving electron produces
A coil having 9 turns carrying a current produces magnetic field $B_1$ at the centre. Now the coil is rewounded into 3 turns carrying same current. Then, the magnetic field at the centre $B_2=$
19. A particle of specific charge $q / m=\pi \mathrm{C} \mathrm{kg}^{-1}$ is projected the origin towards positive $X$-axis with the velocity $10 \mathrm{~ms}^{-1}$ in a uniform magnetic field $\mathbf{B}=-2 \hat{\mathbf{k} T}$. The velocity $\mathbf{v}$ of particle after time $t=\frac{1}{12} \mathrm{~s}$ will be (in $\mathrm{ms}^{-1}$)
The magnetic field at the centre of a circular coil of radius $R$ carrying current $I$ is 64 times the magnetic field at a distance $x$ on its axis from the centre of the coil. Then, the value of $x$ is
A uniform magnetic field of strength $B=2 \mathrm{mT}$ exists vertically downwards. These magnetic field lines pass through a closed surface as shown in the figure. The closed surface consists of a hemisphere $S_1$, a right circular cone $S_2$ and a circular surface $S_3$. The magnetic flux through $S_1$ and $S_2$ are respectively.
A charged particle is subjected to acceleration in a cyclotron as shown. The charged particle undergoes increase in its speed
A positively charged particle $$q$$ of mass $m$ is passed through a velocity selector. It moves horizontally rightward without deviation along the line $$y=\frac{2 m v}{q B}$$ with a speed $$v$$. The electric field is vertically downwards and magnetic field is into the plane of paper. Now, the electric field is switched off at $$t=0$$. The angular momentum of the charged particle about origin $$O$$ at $$t=\frac{\pi m}{q B}$$ is
The torque acting on a magnetic dipole placed in uniform magnetic field is zero, when the angle between the dipole axis and the magnetic field is .........
A proton and an alpha-particle moving with the same velocity enter a uniform magnetic field with their velocities perpendicular to the magnetic field. The ratio of radii of their circular paths is
A metallic rod of mass per unit length $$0.5 \mathrm{~kg} \mathrm{~m}^{-1}$$ is lying horizontally on a smooth inclined plane which makes an angle of $$30^{\circ}$$ with the horizontal. A magnetic field of strength $$0.25 \mathrm{~T}$$ is acting on it in the vertical direction. When a current $$I$$ is flowing through it, the rod is not allowed to slide down. The quantity of current required to keep the rod stationary is
A proton moves with a velocity of $$5 \times 10^6 \hat{\mathbf{\widehat j} m \mathrm{~m}^{-1}}$$ through the uniform electric field, $$\mathbf{\overrightarrow E}=4 \times 10^6[2 \hat{\mathbf{i}}+0.2 \hat{\mathbf{j}}+0.1 \hat{\mathbf{k}}] \mathrm{Vm}^{-1}$$ and the uniform magnetic field $$\mathbf{\overrightarrow B}=0.2[\hat{\mathbf{i}}+0.2 \hat{\mathbf{j}}+\hat{\mathbf{k}}] \mathrm{T}$$. The approximate net force acting on the proton is
A solenoid of length $$50 \mathrm{~cm}$$ having 100 turns carries a current of $$2.5 \mathrm{~A}$$. The magnetic field at one end of the solenoid is
A circular coil of wire of radius $$r$$ has $$n$$ turns and carries a current $$I$$. The magnetic induction $$B$$ at a point on the axis of the coil at a distance $$\sqrt{3} r$$ from its centre is
Which of the following statements proves that Earth has a magnetic field ?
A copper rod $$A B$$ of length $$l$$ is rotated about end $$A$$ with a constant angular velocity $$\omega$$. The electric field at a distance $$x$$ from the axis of rotation is
A strong magnetic field is applied on a stationary electron. Then, the electron
Two parallel wires in free space are $$10 \mathrm{~cm}$$ apart and each carries a current of $$10 \mathrm{~A}$$ in the same direction. The force exerted by one wire on the other [per unit length] is
A toroid with thick windings of $$N$$ turns has inner and outer radii $$R_1$$ and $$R_2$$, respectively. If it carries certain steady current $$I$$, the variation of the magnetic field due to the toroid with radial distance is correctly graphed in
A tightly wound long solenoid has $n$ turns per unit length, a radius $$r$$ and carries a current $$I$$. A particle having charge $$q$$ and mass $$m$$ is projected from a point on the axis in a direction perpendicular to the axis. The maximum speed of the particle for which the particle does not strike the solenoid is
Which of the field pattern given below is valid for electric field as well as for magnetic field?
In the given figure, the magnetic field at $$O$$.
The magnetic field at the origin due to a current element $$i d \mathbf{l}$$ placed at a point with vector position $$\mathrm{r}$$ is
A long cylindrical wire of radius $$R$$ carries a uniform current $$I$$ flowing through it. The variation of magnetic field with distance $$r$$ from the axis of the wire is shown by
A cyclotron is used to accelerate protons $$\left({ }_1^l \mathrm{H}\right)$$ deuterons $$\left({ }_1^2 \mathrm{H}\right)$$ and $$\alpha$$-particles $$\left({ }_2^4 \mathrm{He}\right)$$. While exiting under similar conditions, the minimum $$\mathrm{KE}$$ is gained by
The ratio of magnetic field at the centre of a current carrying circular coil to its magnetic moment is $$x$$, if the current and the radius both are doubled. The new ratio will become
Two long straight parallel wires are a distance $$d$$ part. They carry steady equal currents flowing out of the plane of the paper. The variation of magnetic field $B$ along the line $$x x^{\prime}$$ is given by
A toroid has 500 turns per meter length. If it carries a current of $$2 \mathrm{A}$$, the magnetic energy density inside the toroid is
In a cyclotron a charged particle
The number of turns in a coil of galvanometer is tripled, then
Coersivity of a magnet where the ferromagnet gets completely demagnetized is $$3 \times 10^3 \mathrm{~Am}^{-1}$$. The minimum current required to be passes in a solenoid having 1000 turns per metre, so that the magnet gets completely demagnetized when placed inside the solenoid is
The magnetic fields at the centre O in the given figure is
