When the switch is thrown from the OFF position (open circuit) to the ON position (closed circuit), then neither B nor A and the angle between B and A does not change. Thus, no change in magnetic flux linked with coil occur, hence no electromotive force is produced and consequently, no current will flow in the circuit.

Both a superconducting material and nitrogen are diamagnetic in nature. When a ball of superconducting material is dipped in liquid nitrogen, it behaves as a diamagnetic material. When placed near a bar magnet, it will be feebly magnetised opposite to the direction of magnetising field. 
Because of this,
(i) it will be repelled (i.e. move away from magnet)
(ii) the direction of magnetic moment will be opposite to the direction of magnetic field of bar magnet.

The least distance of discint vision of an average person. (i.e, D) is 25 cm, in order to view an object with magnificaton of 10. 
Here, v = D = 25 cm and u = f
But thr magnification, m = v/u = D/f
\(m=\frac { D }{ f } \Rightarrow f=\frac { D }{ m } =\frac { 25 }{ 10 } =2.5=0.025m\)
\( P=\frac { 1 }{ 0.025 } =40D \ [\therefore \ P=\frac { 1 }{ f } ]\)
This is the required power of lens.

When we are considering a point of sound wavw. The disturbance due to the source propagates in spherical symmetry, that is, in all directions.
       
The formation of wavefront is in accordance with Huygen's principle. So, Huygen's principle is valid for longitudinal sound waves also.

If an ideal capacitor is charged by DC battery, current flows momentarily till capacitor gets fully charged after that no current flows. however, when an AC source is connected, the conduction current, \(I_c=\frac{d q}{d t}\) starts flowing in the connecting wire. As charging polarity of AC current changes, the capacitor is alternatively charged and discharged with time. this causes change in electric field between plates of the capacitor which causes change in electric flux and gives rise to displacement current in the region between plates of cpacitor, as displacement current, \(I_d=\varepsilon_0 \frac{d {\phi}_E}{d t}\) and I_d = I_e at all instants.

(i) As the magnet falls, the magnetic flux linked with the ring increases. This induces emf in the ring which opposes the motion of the falling magnet, hence a < g.
(ii) When current is suddenly switched ON, magnetic flux linked with the solenoid and thus, with metal ring increases. Current is induced in the ring in an anti-clockwise direction (as seen from the top of the ring). Since the direction of flow of current in the ring is opposite to the current in the solenoid, therefore they will repel each other and the ring jumps up.   

Consider the diagram.
Bandwidth = \(\omega _{ 2 }-{ \omega }_{ 1 }\),

Where , \(\omega_1\) and  \(\omega_2\)  correspond to frequencies at which magnitude of  current is \(\frac { 1 }{ \sqrt { 2 } } \) times of maximum value.
\({ I }_{ rms }=\frac { { I }_{ max } }{ \sqrt { 2 } } =\frac { 1 }{ \sqrt { 2 } } \approx 0.7A\)
Clearly, from the diagram, the corresponding frequencies are 0.8 rad/s and rad/s.
\(\triangle \omega \) = B and width = 1.2 - 0.8 = 0.4 rad/s

Now, suppose that the angle between M and B is \(\theta \) .
Troque on magnetic dipole moment M in magnetic field B,
 \({ \tau }^{ ' }=MBsin\theta \)
Two motions will be identical, if
\(pEsin\theta =MBsin\theta \\ pE=MB\\ E=cB\)
Putting this value in Eq.(i), we get
\(pcB=MB\quad \Rightarrow p=\frac { M }{ c } \) 

As, the value of R is increased, the current flowing in the circuit will decrease. And the potential gradient, i.e. potential drop per unit length also decreases, so that the balance length will increase. Thus, J will shift towards B.

When a bird is perched on a bare high power line, the circuit does not get complete between the bird and the earth, therefore, nothing happens to the bird.
When a man standing on ground touches the same line, the circuit between the man and the earth gets completed. As a result, he gets a fatal shock.