Mathematical Problems
1. Magnetic flux of 1.5 × 10-4 Wb is produced when current of 3A flows through a coil
of 600 turns. If the current reduces to zero in 0.06 s, then calculate (i) the induced
electromotive force in the coil, (ii) self-inductance of the coil and (iii) energy stored
in the coil.
2. Magnetic flux of 1.5 × 10-4 Wb is produced when current of 3A flows through a coil
of 600 turns. If the current reduces to zero in 0.06 s, then calculate (i) the induced
electromotive force in the coil, (ii) self-inductance of the coil and (iii) energy stored
in the coil.
3. A steady current of 2A flow through an inductor of 10 Henry inductance. How can
electromotive force of 100V be induced in the coil?
4. The peak value on an alternating current in a circuit is 20A and its frequency is 50
Hz. Find the root mean square value of the current. How long will it take to reach
the peak from the zero value?
5. If the equation of an alternating current is, I = 50 sin 628 t, then find (i) peak value
(ii) frequency and (iii) root mean square value of the current.
6. Calculate the velocity achieved by an electron at rest when it is passed through a
potential difference of 10 kilo volt.
7. An ultraviolet ray of wavelength of 2500 A0 is incident on a metal surface. If the
work function of the metal is 2.3 eV. What is the maximum velocity of the emitted
photoelectron?
8. The work function of platinum is 6.31 eV. What is its threshold frequency? ( h =
6.63 × 10-34 Js )
9. When radiation of frequency of 4 × 1015 Hz is incident on a metal surface, electron
of maximum energy of 3.6 × 10-19 J is emitted. What is the threshold frequency of
that metal?
10. A metal surface is exposed to light of wavelength of 6000 A0 . 1.77 eV is required
to remove an electron. What is the kinetic energy of the fastest electron? What is
the threshold frequency? ( h = 6.63 × 10-34 Js and 1eV = 1.6 × 10-19 J)
11. What time will it take to decay 60% of a piece of radon? Half life of radon is 3.82
days.
12. If 108 numbers of atoms of radon initially remains in a piece of a substance, then
how many atoms will disintegrate in one day? Half life of radon is 4 days.
