A jet plane of wingspan 20m is travelling towards the west at a speed of 400ms$^{-1}$. If the earth's total magnetic field is $4 \times 10^{-4} T$ and the drip angle is $30^\circ$, at that place, the voltage difference developed across the ends of the wing is
A.) 3.2V
B.) 6.4V
C.) 1.6V
D.) 0 V

Hint: To know the direction of induced e.m.f. or current in a straight conductor moved perpendicular to the magnetic field, we use Fleming's right-hand rule.

It stated that the first finger and middle finger of the right hand so that they are mutually perpendicular to each other. If the first finger represents the direction of the magnetic field and represents the direction of motion of the conductor, then the middle finger represents the direction of the induced e.m.f. Of current in the conductor

Complete step by step solution:

It is a question from magnetism.

We know that the e.m.f. Induced rod travelling in a magnetic field is given by Blv.

$e.m.f=Bvl$

Where B is a magnetic field
V is the speed of rod perpendicular to a magnetic field
L is the length of the rod.

We know that span of the wing is 20m
Earth magnetic field is $4\times {{10}^{-4}}T$
And the speed of the jet plane is 400m/s
Drip angle is ${{30}^{0}}$.

We know, velocity perpendicular to the magnetic field is $400\sin ({{30}^{0}})$

Therefore induce e.m.f is given by

$\begin{align}
  & e.m.f=4\times {{10}^{-4}}\times 400\sin ({{30}^{0}})\times 20 \\
 & e.m.f=1.6V \\
\end{align}$

The voltage difference developed across the ends of the wing is 1.6V.

Answer- (C)

Note: The earth behaves as a magnet with the magnetic field pointing approximately from the Geographic South to the north if we cut bar magnet into pieces we find that each piece however small it may be is still a magnetic dipole magnetic monopoles do not exist magnetism has its origin in the calculating charge is within the atoms of any substance.