Figure shows a
capacitor made of two circularplates each of radius 12 cm and separated by5.0
cm. The capacitor is being charged by anexternal source (not shown in figure).
Thecharging current is constant and equal to0.15 A.
(a) Calculate
the capacitance and the rate ofchange of potential difference between
theplates.
(b) Obtain
the displacement current acrossthe plates.
(c) Is Kirchhoff?s
first rule valid at eachplate ofthe capacitor? Explain.
A parallel plate
capacitor (shown in figure)made of circular plates each of radius has
a capacitance . Thecapacitor is
connected to a 230 V a.c. supplywith a (angular) frequency of 300 rad .
(a) What is
the r.m.s. value of the conductioncurrent?
(b) Is the
conduction current equal to thedisplacement current?
(c)
Determine the amplitude of B at a point3.0 cm from the axis between the plates.
A plane electromagnetic wave travels invacuum along z-direction. What can you sayabout the directions of its electric andmagnetic field vectors? If the frequency ofthe wave is 30 MHz, what is its wavelength?
A charged particle
oscillates about its meanequilibrium position with a frequency of.
What is the frequency of theelectromagnetic waves produced by theoscillator?
Suppose that the
electric field amplitude ofan electromagnetic wave is and that
its frequency is . (a)Determine, and
. (b) Findexpressions
for E and B.
The terminology of
different parts of theelectromagnetic spectrum is given in the text.Use the
formula (for
energy of aquantum of radiation : photon) and obtain thephoton energy in units
of for differentparts
of the electromagnetic spectrum. In whatway are the different scales of photon
energiesthat you obtain related to the sources ofelectromagnetic radiation?
In a plane
electromagnetic wave, the electricfield oscillates sinusoidally at a frequency
ofand amplitude .
(a) What is
the wavetehgth of the wave?
(b) What is
the amplitude of the oscillatingmagnetic field?
(c) Show that the average
energy density ofthe E field equals the average energydensity of the B field. .
Suppose that the
electric field part of anelectromagnetic wave in vacuum is .
(a) What is
the direction of propagation?
(b) What is
the wavelength ?
(c) What is
the frequency ?
(d) What is
the amplitude of the magneticfield part of the wave?
(e) Write an
expression for the magnetic fieldpart of the wave.
About 5% of the power of a 100 W lightbulb is converted to visible radiation. Whatis the average intensity of visible radiation?
(a) at a distance of 1 m from the bulb?
(b) at a distance of 10 m?
Assume that the radiation is emitted is o tropically and neglect reflection.
Use the formula to
obtain the characteristic temperature ranges for different parts of the
electromagnetic spectrum. What do the numbers that you obtain tell you?
Given below are some
famous numbersassociated with electromagnetic radiationsin different contexts
in physics State the partof the electromagnetic spectrum to whicheach belongs.
(a) 21 cm
(wavelength emitted by atomichydrogen in interstellar space).
(b) 1057 MHz
(frequency of radiation arisingfrom two close energy levels in hydrogen;known
as Lamb shift.)
(c) 2.7 K
(temperature associated with theisotropic radiation filling all space-thought
to be a relic of the ?big-bang? origin of the universe.)
(d) (double
lines of sodium)
(e) 14.4 keV[energy
of a particulartransition in nucleus
associated witha famous high resolution spectroscopicmethod (Mossbauer
spectroscopy).]