Magnetic flux density - class-XII
Comprehensive quiz covering magnetic flux density, magnetic flux, electromagnetic induction, and related electromagnetic phenomena including electric flux and field calculations.
Questions
A square loop of side 12 cm and resistance 0.60$\Omega$ is placed vertically in the east-west plane. A uniform magnetic field of 0.1 T is setup across the plane in north-east direction. The magnetic field is decreased to zero in 0.6 s at a steady rate. The magnitude of current during this time interval is
- $1.42 \times 10^{-3} A$
- $2.67 \times 10^{-3} A$
- $3.41\times 10^{-3} A$
- $4.21 \times 10^{-3} A$
When the normal to a coil points in the direction of magnetic field (B), then flux is
- a scalar quantity
- a vector quantity
- neither scalar nor vector
- uncertain
Current $i _0$ is being carried by an infinite wire passing through origin along the direction $\hat{i} + \hat{j} + \hat{k}$. Find magnetic field due to the wire at point $(1 m, 0, 0)$.
- $\dfrac{(\mu _0 i)}{(2 \pi)} T$
- $\dfrac{(\mu _0 i)}{(\sqrt{2} \pi)} T$
- $\dfrac{(\mu _0 i)}{(4 \pi)} T$
- $\dfrac{(\sqrt{3} \mu _0 i)}{(2 \sqrt{2} \pi)} T$
A charge q is placed at the centre of a cylinder of radius R and length 2R. Then electric flux through the curved surface of the cylinder is
- $\cfrac { q }{ 2 { \epsilon } _{ 0 } } $
- $\cfrac { q }{ 4 { \epsilon } _{ 0 } } $
- $\cfrac { q }{ \sqrt { 2 } { \epsilon } _{ 0 } } $
- $\cfrac { q }{ 2\sqrt { 2 } { \epsilon } _{ 0 } } $
A Point source generates 10 J of light energy in 2 s. The luminous flux of source is:
- 5 lumen
- 10 lumen
- 50 lumen
- none of these
A cyclotron in which protons are accelerated has a flux density 1.57T. The variation of frequency of electric field is (in Hz)
- $4.8 \times 10 ^ { 8 }$
- $8.4 \times 10 ^ { 8 }$
- $2.5 \times 10 ^ { 7 }$
- $4.8 \times 10 ^ { 6 }$
The electric field potential in space has the form $V(x,y,z)=-2xy+3yz^{-1}$. The electric field intensity $\vec E$ magnitude at the point (-1,1,2) is
- $2 \sqrt{86} units$
- $2\sqrt{163} units$
- $\sqrt{163} units$
- $ \sqrt{86} units$
An iron rod of volume ${ 10 }^{ -4 }{ m }^{ 3 }$ and relative permeability 1000 is placed inside a long solenoid would with. 5 turn ism. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod is:
- 10 ${ Am }^{ 2 }$
- 15 ${ Am }^{ 2 }$
- 20 ${ Am }^{ 2 }$
- 25 ${ Am }^{ 2 }$
Unit of magnetic flux density is
- $weber/metre$
- $weber$
- $weber/m^{2}$
- $ampere/m$
Current in a circular coil having negligible resistance and inductance 0.1 H is increasing at the rate of $1 As^{-1}$. The power generated in the coil when the magnetic flux linked with it is 0.1 Wb will be:-
- 0.05 W
- 0.1W
- 1 W
- 10 W
The magnetic flux density at a point distant $d$ from a long straight current carrying conductor is $B$, then its value at distance $d/2$ will be:
- $4B$
- $2B$
- $B/2$
- $B/4$
The magnetic needle of a tangent galvanometer is deflected at an angle $30$ due to a magnet. The horizontal component of earth's magnetic field $0.34\times 10^{-4}T$ is along the plane of the coil. The magnetic intensity is:
- $1.96\times 10^{-4}T$
- $1.96\times 10^{-5}T$
- $1.96\times 10^{4}T$
- $1.96\times 10^{5}T$
A sphere of radius $R$ and charge $Q$ is placed inside an imaginary sphere of radius $2R$. Whose center coincides with the given sphere. The flux related to the imaginary sphere is:
- $\dfrac {Q}{\in _{0}}$
- $\dfrac {Q}{2\in _{0}}$
- $\dfrac {4Q}{\in _{0}}$
- $\dfrac {2Q}{\in _{0}}$
The flux linked with a coil changes with time according to the equation $\phi$ = a$t^2$ +bt +c. Then SI unit of a is
- Volt
- Volt/sec
- Volt.sec
- Weber
In a circuit a coil of resistance $2,\Omega$, then magnetic flux charges from $2.0,Wb$ to $10.0,Wb$ in $0.2\ sec.$ The charge flow in the coil during this time is:
- $5.0\ C$
- $4.0\ C$
- $1.0\ C$
- $0.8\ C$
Two coils $A$ and $B$ are wound on the same iron core as shown in figure. The number of turns in the coil $A$ and $B$ are $N _{A}$ and $N _{B}$ respectively. Identity the correct statement
- Both the coils have same magnitude of magnetic flux
- The magnetic flux linked are in the ratio $\dfrac{\phi A}{\phi B}=\dfrac{N _{A}}{N _{B}}$
- The induced emf across each coil are in the ratio $\dfrac{E _{A}}{E _{B}}=\left(\dfrac{N _{4}}{N _{B}}\right)^{2}$
- Both the coils have same magnitude of induced emf
The magnetic flux through a stationary loop with resistance R varies during the interval of time T as $\phi = at(T - t)$ ./ The heat generated during this time neglecting the inductance of the loop will be :
- $\dfrac{{{a^2}{T^3}}}{{3R}}$
- $\dfrac{{{a^2}{T^2}}}{{3R}}$
- $\dfrac{{{a^2}T}}{{3R}}$
- $\dfrac{{{a^3}{T^3}}}{{3R}}$
A circular disc of radius $0.2$m isplaced in a uniform magnetic field of induction $\dfrac{1}{\pi}\left(\dfrac {Wb}{m^2}\right)$ in such a way that its axis ,makes an angle of $60^o$ with $\xrightarrow {B}$. The magnetic flux linked with the disc is
- $0.01$ Wb
- $0.02$ Wb
- $0.06$ Wb
- $0.08$ Wb
The magnetic flux through a coil is $4\times 10^{-4} W/b/m^2$ at time $t=0$.It reduces to $10%$ of its original value in 't' seconds.If the induced e.m.f is $0.72 m V,$ then the time t is:
- $0.25 s$
- $0.05 s$
- $0.75 s$
- $1 s$
In a uniform electric field $\vec {E}$ an imaginary cube of edge length $a$ is considered as shown. The outward flux linked with cube surface will be :
- $Ea^{2}$
- $\sqrt{2}Ea^{2}$
- $\sqrt{3}Ea^{2}$
- $2Ea^{2}$
State whether the following two statements are true or false
(i) Li has the same units as that of magnetic flux.
(ii) Li has the units volt-second and magnetic flux has the units coulomb-ohm.
- T T
- F F
- T F
- F T
The ratio of magnetic inductions at the centre of a circular coil of radius a and on its axis at a distance equal to its radius, will be -
- $\frac { 1 }{ \sqrt { 2 } } $
- $\frac { \sqrt { 2 } }{ 1 } $
- $\frac { 1 }{ 2\sqrt { 2 } } $
- $\frac { 2\sqrt { 2 } }{ 1 } $
The sun delivers ${10^3}W/{m^2}$ of electromagnetic flux to the earth's surface. The solar energy incident on the roof in $1$houre will be
- $5.76 \times {10^8}J$
- $5.76 \times {10^7}J$
- $5.76 \times {10^6}J$
- $5.76 \times {10^5}J$
Light with an energy flux of $18 w/cm^2$ falls on a non-reflecting surface at normal incidence. If the surface has an area of $20 cm^2$. Find the average force exerted on the surface during a 30 minute time
- $1.2 \times 10 ^ { - 6 } N$
- $2 .4\times 10 ^ { - 6 } N$
- $2.16 \times 10 ^ { - 3 } \mathrm { N }$
- $1.5\times 10 ^ { - 6 } N$
The electric field in a certain region is $\left( 10\hat { i } +5\hat { j } \right) \times { 10 }^{ 4 }N/C$. What is the flux due to this field over an area of $\left( 3\hat { i } +3\hat { j } \right) \times { 10 }^{ -2 }{ m }^{ 2 }$ in ${ Nm }^{ 2 }/C?$
- $4.5\times { 10 }^{ 3 }$
- $3.5\times { 10 }^{ 3 }$
- $2.5\times { 10 }^{ 3 }$
- $1.5\times { 10 }^{ 3 }$
Current flowing through a long solenoid is varied. Then, magnetic flux density of the magnetic field inside varies ::
- inversely with $I$
- inversely with ${ I }^{ 2 }$
- directly with $I$
- directly with ${ I }^{ 2 }$
A wire of length $'\ell '$ is used to make a circular coil of 'n' no. of turns. A current 'I' passes through the coil. If twice the length of wire is used now to make the coil with turns of same radius, making same current flow through it, the magnetic field at the centre of coil will become.
- 1.5 times than earlier
- 0.5 time than earlier
- 2 times than earlier
- 4 time than earlier
The magnetic flux linked with a coil is given by the equation $ \phi = 5t^2 + 3t + 6 $. The induced e.m.f. in the coil in the fourth second will be
- 20 V
- 40 V
- 10 V
- 80 V
A closely wound flat circular coil of 25 turns of wire has diameter of =f 10 cm and carries a current of 4 amperes. determine the magnetic flux density at the centre of the coil:-
- $ 1.679 \times 10^{-5} T $
- $ 2.028 \times 10^{-4} T $
- $ 1.257 \times 10^{-3} T $
- $ 1.512 \times 10^{-6} T $
The magnetic flux linked with a coil, in webers, is given by the equation $\phi =4t^{2}-3t+7$. Then the magnitude of induced emf at 2 sec will be....
- 15 v
- 19 v
- 17 v
- 21 v
Magnetic field intensity at the centre of coil of 50 turns, radius 0.5 m and carrying a current of 2 A is
- $0.5 \times 10^{-5}T$
- $3 \times 10^{-5}T$
- $1.25 \times 10^{-4}T$
- $4 \times 10^{-5}T$
Select the incorrect option
- Luminous flux and radiant flux have same dimensions
- Luminous flux and luminous intensity have same dimensions
- Radiant flux and power have same dimension
- Relative luminosity is a dimensionless quantity
A current carrying wire produces a magnetic field in its surrounding space.
The S.I. unit of magnetic flux density is
- Henry
- Tesla
- $AM^2$
- A-m
The dimensional formula of magnetic flux is ___________.
- $\left[ M{ L }^{ 2 }{ T }^{ -2 }{ A }^{ -1 } \right] $
- $\left[ M{ L }^{ 2 }{ T }^{ -3 }{ A }^{ -1 } \right] $
- $\left[ { M }^{ -1 }{ L }^{ -2 }{ T }^{ 2 }{ A }^{ 1 } \right] $
- $\left[ M{ L }^{ 3 }{ T }^{ -2 }{ A }^{ -1 } \right] $
In an experiment to measure the velocity of electrons, an electric field $(E)$ and a magnetic field $(B)$ are employed to produce zero deflection. Then :
- The two fields are parallel and the velocity is given by $BE$
- The two fields are perpendicular and the velocity is given by $E/B$
- The two fields are parallel and the velocity is given by $E/B$
- The two fields are perpendicular and the velocity is given by $BE$
Write the dimensions of Magnetic flux in terms of mass, time, length and charge.
- $[M^1L^2T^{-1}Q^{-2}]$
- $[M^1L^2T^{-1}Q^{-1}]$
- $[M^1L^3T^{-1}Q^{-1}]$
- $[M^4L^2T^{-1}Q^{-1}]$