Permeability

Q.

The refractive index of a medium ‘x’ with respect to a medium ‘y’ is 2/3 and the refractive index of medium ‘y’ with respect to a medium ‘z’ is 4/3. Find the refractive index of medium ‘z’ with respect to medium ‘x’. If the speed of light in medium ‘x’ is $3\times {10}^{8}m/s$, calculate the speed of light in medium ‘y’.

Q.

What is absolute and relative permeability?

Q.

If a diamagnetic substance is brought near north or south pole of a bar magnet, it is

Q. White light is passed through the double slit and interference pattern is observed on a screen $2.5\text{m}$ away. The separation between the slits is $0.5\text{mm}$. The first violet and red fringes are formed at distances of $2\text{mm}$ and $3.5\text{mm}$ away from the central white fringe respectively. Calculate wavelengths of red and violet light.

1. $800\text{nm}$ and $400\text{nm}$
2. $350\text{nm}$ and $200\text{nm}$
3. $750\text{nm}$ and $350\text{nm}$
4. $700\text{nm}$ and $400\text{nm}$

Q. A plane electromagnetic waves travels in a medium of relative permeability $1.61$ and relative permittivity $6.44$. If magnitude of magnetic intensity is $4.5\times {10}^{-2}{\text{Am}}^{-1}$ at a point, what will be the approximate magnitude of electric field intensity at that point?
(Given: Permeability of free space ${\mu }_0=4\pi \times {10}^{-7}{\text{NA}}^{-2}$, speed of light in vacuum $c=3\times {10}^8{\text{ms}}^{-1}$)

1. $8.48{\text{Vm}}^{-1}$
2. $6.75\times {10}^6{\text{Vm}}^{-1}$
3. $16.96{\text{Vm}}^{-1}$
4. $2.25\times {10}^{-2}{\text{Vm}}^{-1}$

Q. A ray of laser of a wavelength $630\text{nm}$ is incident at an angle of ${30}^{\circ }$ at the diamond-air interface. It is going from diamond to air. The refractive index of diamond is $2.42$ and that of air is $1.$ Choose the correct option.

1. refraction is not possible
2. angle of refraction is ${53.4}^{\circ }$
3. angle of refraction is ${24.41}^{\circ }$
4. angle of refraction is ${30}^{\circ }$

Q. A magnetising field of 2*10^3 produces a magnetic flux density 8 pi tesla in an iron rod the relative permeability of rod will be

Q. What should be the value of the refractive index $n$ of a glass rod placed in air so that the light entering through flat surface of the rod does not cross the curved surface of the rod?

1. $n=\frac{1}{\sqrt{2}}$
2. $n\le \sqrt{2}$
3. $n\ge \frac{1}{\sqrt{2}}$
4. $n\ge \sqrt{2}$

Q. ${}^{\prime }{n}^{\prime }$ transparent slabs of refractive index $1.5$ each having thickness $1\text{cm},2\text{cm},...n\text{cm}$ are arranged one over the other. A point object is seen through this combination from top with perpendicular light. If the shift of the object by combination is $5\text{cm}$. Then the value of ${}^{\prime }{n}^{\prime }$ is

1. $5$
2. $4$
3. $3$
4. $2$

Q. Unit of intensity of magnetisation is ampere per meter. how?

Q. A uniform magnetic field, parallel to the plane of the paper existed in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by

1. Figure (A)
2. Figure (B)
3. Figure (C)
4. Figure (D)

Q. The core of a toroid having 3000 turns has inner and Outer radii of 16cm and 17cm respectively. The magnetic field in the core for a current of 0.07A is 2.5T. What is relative permeability of the core

Q. The ratio of thickness of plates of two transparent mediums A and B is 6 : 4. If light takes equal time in passing through them, then refractive index of B with respect to A will be

1. 1.4
2. 1.75
3. 1.33
4. 1.5

Q. Assertion $\left(A\right)$ : Electromagnets are made of soft iron.

Reason $\left(R\right)$ : Coerctivity of soft iron is small.

1. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is the correct explanation of $\left(A\right)$
2. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is not the correct explanation of $\left(A\right)$
3. $\left(A\right)$ is true but $\left(R\right)$ is false.
4. $\left(A\right)$ is false but $\left(R\right)$ is true.

Q. Magnetic materials used for making permanent magnets $\left(P\right)$ and magnets in a transformer $\left(T\right)$ have different properties of the following, which property best matches for the type of magnet required?

1. $T$ : Large retentivity, small coercivity
2. $P$ : Small retentivity, large coercivity
3. $T$ : Large retentivity, large coercivity
4. $P$ : Large retentivity, large coercivity

Q. The length of a vertical pole at the surface of a lake of water $(\mu =\frac{4}{3})$ is $24\text{cm}$. Then, for a fish just below the water surface, the tip of the pole appears to be at

1. $18\text{cm}$ above the water surface
2. $24\text{cm}$ above the water surface
3. $30\text{cm}$ above the water surface
4. $32\text{cm}$ above the water surface

Q. How to derive the dimensional formula for magnetic flux ?

Q. In a Young's double slit experiment, the slits $S_1$ and $S_2$ are illuminated by a parallel beam of light of wavelength $4000\dot{A}$ from the medium of refractive index ${\mu }_1=1.2$. A thin film of thickness $1.2\mu \text{m}$ and refractive index $\mu =1.5$ is placed in front of $S_1$ perpendicular to the path of light. The refractive index of the medium between the plane of slits and screen is ${\mu }_2=1.4$. If the light coming from $S_1$ and $S_2$ have equal intensity $I$, then the intensity at the geometrical centre of screen $O$ is:

1. $0$
2. $2I$
3. $4I$
4. $I$

Q. A cylindrical conductor of radius R carries a current ′i′. The value of magnetic field at a point which is R/4 distance inside from the surface is 10 T. Find the value of magnetic field at point which is 4R distance outside from the surface.

1. $\frac{80}{3}T$
2. $\frac{4}{3}T$
3. $\frac{40}{3}T$
4. $\frac{8}{3}T$

Q. The area of hysteresis material of a loop of a material is equivalent to 200 J. When 5 kg material is magnetised by an alternating field of 50 Hz then energy lost in one hour will be (density of material is 8 g/cm3

Q. A metallic ring with a cut is held horizontally and a magnet is allowed to fall vertically through the ring then acceleration of this magnet is

Q. Draw a graph between intensity of magnetization and magnetic intensity of non - magnetized ferromagnetic substance and explain magnetic retentivity and magnetic coercivity from graph. What is hysteresis with graph?

Q.

Write some examples of magnetic susceptibility?

Q. A glass slab ($\mu =1.5)$ of thickness $4\text{cm}$ is pressed against newspaper, the distance by which letter of the paper are seen raised against the paper by someone who is looking at letters along normal to the slab is

1. $1\text{cm}$
2. $\frac{2}{3}\text{cm}$
3. $\frac{4}{3}\text{cm}$
4. $\frac{8}{3}\text{cm}$

Q. For different substances, hysteresis $(B-H)$ curves are given as shown in figure. For making an electromagnet, which of the following is most suitable?

1. Both $A$ and $B$
2. Only $B$
3. Only $C$
4. Both $B$ and $C$

Q.

What is Curie point of a magnet?

Q. Find the position of image ?

1. $+20\text{cm}$
2. $+45\text{cm}$
3. $-45\text{cm}$
4. $+30\text{cm}$

Q. The length of a vertical pole above the surface of a lake of water $(\mu =\frac{4}{3})$ is $24\text{cm}$. Then for a fish just below the water surface, the tip of the pole appears to be

1. $18\text{cm}$ above the surface of water.
2. $24\text{cm}$ above the surface of water.
3. $30\text{cm}$ above the surface of water
4. $32\text{cm}$ above the surface of water

Q. The relation between magnetic susceptibility ${\chi }_m$ and relative permeability ${\mu }_r$ is

1. ${\chi }_m={\mu }_r$
2. ${\chi }_m-1={\mu }_r$
3. ${\mu }_r=1+{\chi }_m$
4. ${\mu }_r=1-{\chi }_m$

Q.

Dimensional formula for permeability