Magnetic Flux and Magnetic Flux Density

Q.

Light with an energy flux$18W{m}^{-3}$ falls on a non-reflecting surface at normal to the surface. If the surface has an area of$20m^2$. The average force exerted on the surface $30minutes$ is

1. $6·48x{10}^{5}N$

2. $3·60x{10}^{2}N$

3. $1·2x{10}^{-6}N$

4. $2·16x{10}^{-3}N$

Q.

What is the definition of magnetic flux?

Q. Magnetic flux is maximum when the angle between the magnetic field and the normal to the plane of finite area is $0^{\circ }$.

1. True
2. False

Q. The units of magnetic flux density is ______.

1. $\text{T}esla$
2. $\text{W}eber/(metre{)}^2$
3. $\text{W}eber/(ampere{)}^2$
4. $\text{T}esla-metre$

Q.

A rod $AB$ slides on a V-shaped wire with speed $v$as shown, such that at any time $OA=OB=l$. The magnetic field in the region is perpendicular downwards and has strength B, the induced emf in the rod is

Q.

Briefly explain the change in flux due to rate of change of area?

Q. Why aurora forms near North pole and South pole only?

Q. The solar constant is equivalent to___ in 12 hours of time.

Q. Light with an energy flux of $18w/c{m}^2$ falls on a non-reflecting surface at normal incidence. If the surface has an area of $20c{m}^2$. Find the average force exerted on the surface during a 30 minute time

1. $1.2\times {10}^{-6}N$
2. $2.4\times {10}^{-6}N$
3. $2.16\times {10}^{-3}N$
4. $1.5\times {10}^{-6}N$

Q. The dimensional formula of magnetic flux is ___________.

1. $\left[M{L}^2{T}^{-2}{A}^{-1}\right]$
2. $\left[M{L}^2{T}^{-3}{A}^{-1}\right]$
3. $\left[M^{-1}{L}^{-2}{T}^2{A}^1\right]$
4. $\left[M{L}^3{T}^{-2}{A}^{-1}\right]$

Q. A Point source generates 10 J of light energy in 2 s. The luminous flux of source is:

1. 10 lumen
2. 5 lumen
3. 50 lumen
4. none of these

Q. The relation between $\left[E\right]$ and $\left[B\right]$ is

1. $\left[E\right]=\left[B\right]\left[L\right]\left[T\right]$
2. $\left[E\right]=\left[B\right]\left[L{]}^{-1}\right[T]$
3. $\left[E\right]=\left[B\right]\left[L{]}^{-1}\right[T{]}^{-1}$
4. $\left[E\right]=\left[B\right]\left[L\right][T{]}^{-1}$

Q. In a circuit a coil of resistance $2\Omega$, then magnetic flux charges from $2.0Wb$ to $10.0Wb$ in $0.2sec.$ The charge flow in the coil during this time is:

1. $5.0C$
2. $4.0C$
3. $1.0C$
4. $0.8C$

Q. A particle enters a magnetic field at right angles as shown.
The direction of force acting on the particle is into the page. The charged particle is a/an:

1. Proton
2. Neutron
3. Electron
4. Alpha particle

Q. A current carrying wire produces a magnetic field in its surrounding space.
The S.I. unit of magnetic flux density is

1. Henry
2. $A{M}^2$
3. Tesla
4. A-m

Q. A charge $+Q$ is located somewhere inside a vertical cone such that the dept of the charge from the free surface of the cone is $H$. It is formed that the flux associated with the cone with thw curved surface is $\frac{3Q}{5{ϵ}_0}$.
If the charge is raised vertically through a height $2H$ then the flux through the curved surface is

1. $\frac{3Q}{5{ϵ}_0}$.
2. $\frac{2Q}{5{ϵ}_0}$.
3. $\frac{4Q}{5{ϵ}_0}$.
4. Zero.

Q. The total magnetic induction at point O due to curved portions and straight portion in the following figure, will be

1. $\frac{{\mu }_{0}i}{2\pi r}[\pi -\varphi +tan\varphi ]$
2. $\frac{{\mu }_{0}i}{2\pi r}$
3. $\frac{{\mu }_{0}i}{\pi r}[\pi -\varphi +tan\varphi ]$
4. 0

Q. The magnetic flux linked with a coil varies as $\varphi =3t^2+4t+9$ . what is the magnitude of the emf at $t=2s$ ? $\varphi$ is in Wb.

Q. Which of the following is an unit of magnetic field intensity?

1. Tesla

2. Farad

3. Watt

4. Mho

Q. This section contains 1 Matrix Match type question, which has 2 Columns (Column I and Column II). Column I has four entries (A), (B), (C) and (D), Column II has four entries (P), (Q), (R) and (S). Match the entries in Column I with the entries in Column II. Each entry in Column I may match with one or more entries in Column II.
इस खण्ड में 1 मैट्रिक्स मिलान प्रकार का प्रश्न है, जिसमें 2 कॉलम (कॉलम I तथा कॉलम II) हैं। कॉलम I में चार प्रविष्टियाँ (A), (B), (C) तथा (D) हैं, कॉलम II में चार प्रविष्टियाँ (P), (Q), (R) तथा (S) हैं। कॉलम I में दी गयी प्रविष्टियों का मिलान कॉलम II में दी गयी प्रविष्टियों के साथ कीजिए। कॉलम I में दी गयी प्रत्येक प्रविष्टि का मिलान कॉलम-II में दी गयी एक या अधिक प्रविष्टियों के साथ हो सकता है।

Magnetic flux associated with a circular coil of resistance 5 Ω changes with time as shown in figure. If flux outward to the plane of paper is taken as positive, then match the information given in Column-I to the information given in Column-II and choose the appropriate answer.

5 Ω प्रतिरोध की एक वृत्तीय कुण्डली से सम्बद्ध चुम्बकीय फ्लक्स, समय के साथ चित्रानुसार परिवर्तित होता है। यदि कागज के तल से बाहर की ओर फ्लक्स को धनात्मक लिया जाए, तब कॉलम-I में दी गई सूचना का मिलान कॉलम-II में दी गई सूचना के साथ कीजिए और सही उत्तर चुनें।

	Column (कॉलम)-I		Column (कॉलम)-II
(A)	At t = 1 s induced current is t = 1 s पर प्रेरित धारा है	(P)	Clockwise दक्षिणावर्त
(B)	At t = 5 s induced current is t = 5 s पर प्रेरित धारा है	(Q)	Anticlockwise वामावर्त
(C)	At t = 15 s induced current is t = 15 s पर प्रेरित धारा है	(R)	Zero शून्य
(D)	At t = 9 s induced current is t = 9 s पर प्रेरित धारा है	(S)	2 A (magnitude) 2 A (परिमाण)

1. A-PRS, B-QR, C-P, D-PQS
2. A-PQS, B-PR, C-QS, D-QRS
3. A-PS, B-R, C-PS, D-QS
4. A-QS, B-PS, C-R, D-PS

Q. A very long cylindrical wire of radius R carries a current $I_0$ uniformly distributed across the cross-section of the wire, calculate the magnetic flux through a rectangle that has one side of length w s running down the centre of the wire and another side of length R, shown in figure

1. $\frac{{\mu }_0{I}_0\times wR}{4\pi }$
2. $\frac{{\mu }_0{I}_{0}w}{4\pi }$
3. $\frac{{\mu }_0{I}_{0}R}{4\pi w}$
4. None of these

Q. The magnetic flux linked with a coil, in webers, is given by the equation $\varphi =4t^2-3t+7$. Then the magnitude of induced emf at 2 sec will be....

1. 15 v
2. 19 v
3. 13 v
4. 21 v

Q. Which of the following area has a maximum magnetic flux density? (Assume both areas $A$ and $B$ to be equal)

1. $B$
2. $A$
3. $A$ = $B$
4. Cannot be determined

Q. A closely wound flat circular coil of $25$ turns of wire has diameter of $10cm$ and carries a current of $4$ amperes. determine the magnetic flux density at the centre of the coil:-

1. $1.257\times {10}^{-3}T$
2. $1.512\times {10}^{-6}T$
3. $1.679\times {10}^{-5}T$
4. $2.028\times {10}^{-4}T$

Q. $A$ and $B$ are two concentric circular conductors of centre $O$ and carrying currents $I_1$ and $I_2$ as shown in the adjacent figure. If ratio of their radii is $1:2$ and ratio of the flux densities at $O$ due to $A$ and $B$ is $1:3$, then the value of $I_1/I_2$ is:

Q. 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 $0.72mV,$ then the time t is:

1. $0.25s$
2. $0.05s$
3. $0.75s$
4. $1s$

Q. What are the units of magnetic permeability?

1. $Wb{A}^{-1}{m}^{-1}$
2. $Wb{A}^{-1}m$
3. $WbA{m}^{-1}$
4. $W{b}^{-1}Am$

Q. When the normal to a coil points in the direction of magnetic field (B), then flux is

1. a scalar quantity
2. a vector quantity
3. neither scalar nor vector
4. uncertain

Q. A closely wound flat circular coil of $25$ turns of wire has diameter of $5$cm which carries current of $4$ amperes, the flux density at the centre of a coil will be

1. $1.256\times {10}^{-3}$ tesla
2. $1.679\times {10}^{-5}$ tesla
3. $2.28\times {10}^{-4}$ telsa
4. $1.512\times {10}^{-5}$ telsa

Q. A long solenoid with $10$ turns per cm has a small loop of area 3 $C{m}^2$ placed inside, normal to the axis of the solenoid. If the current carried by the solenoid changes steadily form $2A$ to $4A$ in $0.2s$, what is the induced voltage in the loop, while the currect is changing?

1. $4.2\times {10}^{-8}$
2. $2.8\times {10}^{-8}$
3. $7.3\times {10}^{-6}$
4. $3.8\times {10}^{-6}$