Magnetic Fields and Electromagnetism - Class XII
Covers magnetic field calculations, charged particle motion in magnetic fields, electromagnetic induction, and magnetic domains in materials
Questions
If E and B denote electronic and magnetic field respectively, which of the following is dimensionless?
- $\sqrt { { \mu } _{ 0 }{ \varepsilon } _{ 0 } } \dfrac { E }{ B } $
- $ { { \mu } _{ 0 }{ \varepsilon } _{ 0 } } \dfrac { E }{ B } $
- ${ \mu } _{ 0 }{ \varepsilon } _{ 0 }{ \left( \dfrac { B }{ E } \right) }^{ 2 }$
- $\dfrac { E }{ { \varepsilon } _{ 0 } } \dfrac { { \mu } _{ 0 } }{ B } $
Ratio of magnetic fields at 10 cm and 20 cm from a infinitely long current carrying wire is
- 1 : 2
- 1 : 4
- 2 : 1
- 4 : 1
A large metal sheet carries an electric current along its surface. Current per unit length is $\lambda $. Magnetic field near the metal sheet is
- $\dfrac{\lambda { \mu } _{ 0 }}{2} $
- $\dfrac{\lambda { \mu } _{ 0 }}{2 \pi} $
- $\lambda { \mu } _{ 0 }$
- $ { \mu } _{ 0 }2\lambda \pi $
A particle of charge $q$ and mass $m$ starts moving from origin under the action of an electric field $\vec { E }$=$E _ { 0 } \vec i $ and magnetic field $\vec { B }$=$B _ { 0 } \vec k $ . Its velocity at $( x , 3,0 )$ is $( 4 i + 3 i )$ , the value of $x$ is:
- $\dfrac { 36 E _ { o } B _ { 0 } } { q m }$
- $\dfrac { 25 m } { 2 q E _ { 0 } }$
- $\dfrac { 10 m } { q E _ { o } }$
- $\dfrac { 25 E _ { 0 } B _ { 0 } } { m }$
Pick correct statements from among the following :
a) Electric field and magnetic field are basically independent
b) Electric field and magnetic field are to aspects of the electromagnetic field
c) Electric field and magnetic field may be produced by charge at rest
d) A moving charge produces both electric and magnetic fields
- a and b are correct
- b and d are correct
- b, c and d are correct
- a, c and d are correct
Two particles having the same specific change (q/m) enter a uniform magnetic field with the same speed but at angles of $30^ \circ$ and $60^\circ$ with the field. Let a, b and c be the ratios of their pitches, radii and periods of their helical paths respectively, then
- $abc = 1$
- $a + b = 2 \sqrt c$
- $a^2 = c$
- $ab = c$
In a given region a charge particle is moving under the effect of electric and magnetic field with uniform velocity $\vec{v}=(\hat{i}+\hat{j}-\hat{k})$ m/s and magnetic field is given as $\vec{B}=(2\hat{i}+\hat{j}-2k)T$. The electric field is given as?
- $({i}+{j}-{k})$ V/m
- $({i}-{j}+{k})$ V/m
- $({i}+k)$ V/m
- $(-{i}-{k})$ V/m
A long, straight, $non-$ conducting string, painted with a charge density of $40\mu\ c/m$, is pulled along its length at a speed of $300\ m/s$. The magnetic field at a normal distance of $5\ mm$ from the moving string is $4.8\times {10}^{-1}\ T$
- $4.8\times {10}^{-1}\ T$
- Zero
- $\infty$
- Cannot be found
Two concentric circular coils of $10$ turns each are situated in the same plane. Their radii are $20$ cm and $40$ cm and carry currents of $0.2$ A and $0.3$ A respectively in opposite directions. The net magnetic induction field at their common centre is
- $\cfrac {35\mu _0}{4}$
- $\cfrac {5\mu _0}{4}$
- $\cfrac {7\mu _0}{8}$
- $\cfrac {\mu _0}{80}$
A coil having resistance $40 \Omega$, number of turns 100 and radius 6 mm is connected to an ammeter of resistance $160 \Omega$. The coil is placed perpendicular to the magnetic field. When the coil is taken out of the field, a charge of $32 \mu C$ passes through it. The intensity of magnetic field will be
- 6.55 T
- 5.66 T
- 0.655 T
- 0.566 T
In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to other. A charged particle is released from rest in this region. The path of the particle will be a:
- circle
- helix
- straight line
- ellipse
The magnetic lines of force like electrical lines of force
- Are closed
- Are not closed
- Are open
- Are not open
Assertion: Basic difference between electric lines and magnetic lines of force is that former are discontinuous and the latter are continuous
Reason: No electric lines of forces exit inside charged conductor but magnetic lines do exist inside magnet
- Both A and R are true and R is the correct explanation of A
- Both A and R are true and R is not correct explanation of A
- A is true, but R is false
- A is false, but R is true
If a charged particle goes unaccelerated in a region containing electric and magnetic fields:
- ${\vec E}$ must be parallel to ${\vec B}$
- ${\vec V}$ must be perpendicular to Electric field
- ${\vec V}$ must be parallel to ${\vec B}$
- $E$ must be equal to $vB$.
An AC rms voltage of 2$\mathrm { V }$ having a frequeney of 50$\mathrm { KH }$ is applied to a condenser of capacity of 10 $\mu F$ The maximum value of the magnetic field between the plates of the condenser if the radius of plate is 10$\mathrm { cm }$ is
- 0.4$\pi \mu T$
- 4$\pi \mu T$
- 4$\mu T$
- 40$\pi \mu T$
The magnetic fields of atoms in a material are grouped together and aligned to form _________.
- Strong magnetic fields
- An area of magnetic field
- A region called magnetic domain
- A bar magnet
The smallest magnet available is ___________.
- a bar magnet with an area of $1 mm^2$
- a spinning electron
- a magnetic dipole
- a molecule or atom with a magnetic dipole
The magnetic domains of an unmagnetised object are found ___________.
- Parallel to each other
- Perpendicular to each other
- Pointing towards south
- Pointing in different direction
The primary origin of magnetism lies in the
- atomic current and intrinsic spin of electrons.
- polar and non polar nature of molecules.
- pauli exclusion principle.
- electronegative nature of materials