Karachi Board ( BSEK)
Note: For complete questions use the book.
Q.14.1 What is flux
density and how is it related with the number of lines of induction expressed
in Weber?
Ans. Magnetic flux density B is the magnetic flux per unit
area (B=φ/A).and its unit of flux density is Weber per meter square or Tesla
(T).The number of magnetic line of forces passes through surface is also known
as magnetic flux density. Each line is known as Weber.
Q.14.2 Charged
particles fired in vacuum tube hit a fluorescent screen. Will it be possible to
know whether they are positive or negative?
Ans. Yes it is possible .it can be found by applying
magnetic field perpendicular to the motion of particle and then the deflection
can be observed. The positive charge in an inward filed will deflect upward.
Q.14.3 Beams of
electron……………………is doubled?
Ans. The radius of circular path of particle in a magnetic
field is r=mv/qb. Which shows that is
directly related to the mass but deflection is inversely related to the
mass>so the electron is lighter and will be deflected more. and if the
velocity is doubled the radius will be doubled.
Q.14.4 A circular
loop of wire hangs………. Earth’s magnetic field?
Ans. The front face of the coil turns in the direction of
geographic North Pole. (Left hand Rule)
Q.14.5 Imagine that
the room in…………………..magnetic origin?
Ans. The direction of current in the loop, as viewed from
the above will be clock wise.(left hand rule)
Q.14.6 Two identical
loops…….machine generates?
Ans. The copper and aluminum has different conductivities,
they show different behavior in the induction. Copper having the higher
conductivity will have the large e m f.
The electric generator does not generate electricity it is
already present in the conducting coil.
They convert mechanical energy in to electrical energy.
Q.14.8 Derive the
general equation…….. in a magnetic field?
Ans. As we know that
F=q(v x B)
Work done=
W=F.L =q(v x B).L
Now V=W/q =q(V x
B).L /q=(v x B).L
Or V= - vBL sinθ b/c (cos 180=-1)
Q.14.9 What is the
mechanism of ………………..loss reduced?
Ans. The electromagnetic induction is the responsible for
the transfer of energy. It works on the principle of mutual induction.(Explain
the process of mutual induction)
