DASHAIN VACATION
HOMEWORK
Department of physics
Class 12
2074
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Use separate
copy to do H.W (do not use rough , thin type of copies.do not use loose sheet)
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Underline with pencil
after each question
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Make your handwriting
best.
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You are requested to
bring H.W on first day of college. H.W will be collected by CR. Students
securing grade other than A and B will have to do H.W again within seven days
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Please completely
avoid coping H.W. Try to do yourself
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Prepare H.W very well
so that it becomes useful in final term examination.
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If there are any
questions from untaught portion, you don't need to do it.
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Do not aim to do all
questions within few days, divide all questions with your holidays and solve
daily.
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Try your best to solve
all the questions
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You can complete this
H. W. within 15 days. Remaining 15 days are your real holidays.
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Enjoy while doing
homework, do not take it as burden.
Attempt all the questions:
1.
Resistors R1 and
R2 are connected in series to an emf source that has negligible
internal resistance. What happens to the current through R1 when
a third resistor R3 is connected in parallel with R2?
2.
What is the difference
between an emf and a potential difference? Under what circumstances are the
potential difference between the terminals of a batter and the battery equal to
each other?
3.
A voltmeter has high
resistance. Explain why?
4.
A cylindrical rod has
resistance R. If we double its length and diameter, what is its resistance in terms
of ‘R’?
5.
Why does an electric
bulb nearly always burn out just as you turn on the light, almost never while
the light is shining?
6.
Can the potential
difference between the terminals of a battery ever be opposite in direction to
the emf?
7.
“Good thermal
conductors are also good electrical conductor” If so, why don’t the connecting
wires that are used to connect heater get hot by conduction of heat from the
heating element?
8.
Two copper wires of
different diameters are joined end – to – end. If a current flows in the wire
combination, what happens to the drift velocity of the electrons when they move
from the larger – diameter wire to the smaller – diameter wire?
9.
When the ends of a
wire are connected to a battery, initially the current is slightly larger, but
soon it decreases slowly and becomes steady at a lower value although the emf
of the battery remains unchanged. Explain.
10.
Is there any
difference between “resistance of a wire” and “resistivity of wire”? Explain
11.
Two bulbs of different
wattage are connected in series. Which buib will glow brighter? Why?
12.
Batteries are
always labeled with their emf. Would it also be appropriate to put a
label on batteries stating how much current they provide? Why or why not?
13.
Sketch the symbols of
“a capacitor”, “an inductor”, “emf of a cell” and “a resistor”
14.
Give an example of non
ohmic conductor and present its current voltage characteristic graph.
15.
What is the ratio of
maximum to minimum resistance obtainable from n wires of resistance R each?
16.
Why is it essential
that the resistance of a voltmeter by very high?
17.
An ammeter is always
connected in series. Why?
18.
Distinguish between
resistance and resistivity of material.
19.
Long distance electric
power, transmission lines always operate at very high voltage, sometime as much
as 750 KV. What are the advantages of such high voltages?
20.
The energy that can be
extracted from a storage battery is always less that the energy that goes into
it while charging. Why?
21.
The resistance of an
ammeter mush essentially be very small. Why?
22.
A wire is stretched to
double its length. What happens to its resistance?
23.
Why do electrons
acquire a steady drift velocity?
24.
You are given 2 wires
each of resistance R. what is the ration of maximum to minimum resistance that
can be obtained from these wires?
25.
Is terminal p.d.
always greater than its emf?
26.
Can the potential
difference across a battery be greater than its emf?
27.
Define drift velocity
of electrons. Establish a relation between drift velocity of electrons and
current density in the conductor.
28.
Explain the theory of
a) series and b) parallel combinations of resistances in an electric circuit
29.
What is meant by a
shunt? How will you convert a galvanometer into an ammeter?
30.
State and explain
Ohm’s law. Two resistors are connected in parallel and third be connected in
series with the combination of parallel resistors. If this combination be
connected with a battery of the negligible internal resistance find the
potential difference across each resistor.
31.
In the given figure,
the current through the 3Ω resister is 0.8 A. Find the potential drop across 4Ω
resister.
32.
A cell of emf 18
V has an internal resistance of 3Ω. The terminal p. d. of the battery becomes
15 V when connected by a wire. Find the resistance of the wire.
33.
A potential difference
of 4.5 V is applied between the ends of wire that is 2.5 m long and has radius
of 0.654 mm. The resulting current through the wire is 17.6 A. What is the
resistivity of the wire?
34.
A tightly coiled
having 75 coils, each 3.50 cm in diameter, is made of insulated metal wire 3.25
mm in diameter. An ohm meter connected across its opposite end reads 1.7Ω. What
is the receptivity of the metal?
35.
A voltmeter coil has
resistance 50Ω and a resister of 1.15K Ω is connected in series. It can read
potential differences up to 12 volts. If the same coil is used to
36.
Construct an ammeter
which can measure currents up to 2A,what should be the resistance of the shunt
used?
37.
In the given figure,
when switch s is open, the voltmeter v reads 3.08v . when the switch is
closed, the voltmeter reading drops to 2.97v, and the ammeter A reads 1.65A
Find the emf, the internal resistance of the battery and the resister R. Assume
that the two meters are ideal.
38.
A resister of 500 Ohms
and one of 2000 Ohms are placed in series with a 60 volt supply. What will be
the reading on a voltmeter of internal resistance 2000 Ohmns when placed across
(i) The 500Ω resistor and (ii) The 2000Ωresister?
39.
What is the potential
difference across 100Q resistor in the circuit given below
40.
41.
Twelve cells each of
emf 2 V and of internal resistance 0.5 ohm are arranged in a battery of n rows
and an external resistance 0.4 ohm is connected to the poles of the battery.
Estimate the current flowing through the resistance in terms of n.
42.
As shown in the
figure, a battery of emf24V and internal resistance r is connected to a circuit
containing two parallel resistors of 3Ωand 6Ω in series with an 8Ω resistor.
The current flowing in the 3Ω is 0.8A. calculate the current in the 6Ω resistor
and the internal resistance of the cell
43.
44.
A battery of
emf1.5V has a terminal p. d of 1.25V when a resistor of 25Ω is joined to it.
Calculate the current flowing, the internal resistance and terminal p. d. when
a resistance of 10Ω replaces 25Ω resistor.
45.
In the given circuit,
calculate the potential difference between the point B and D.
46.
47.
Why do we prefer a
potential meter to measure emf of a cell rather than a voltmeter?
48.
Distinguish
between wave fronts and wavelets.
49.
A normally incident
wave front does not deviate, when it travels from one medium to another.
Explain
50.
Can Snell's law be
verified from wave theory? Explain with figure only.
51.
What is wave front?
52.
What is Huygen's
principle?
53.
When monochromatic
light incidents on a surface, the reflected and refracted wave will have same
frequency. Why?
54.
State Huygen's
principle/ does it apply to sound waves in air?
55.
Which parameters
of light does not change on refraction?
56.
Differentiate between
a plane wave front and a spherical wave front.
57.
State and explain
Huygen's principle. Derive the law of reflection on the basis of this
principle.
58.
Describe Michelson's
methods for the determination of speed of light.
59.
State and explain
Huygen's principle and use it to verify Snell's law.
60.
Describe Foucault's
Method to determine the velocity of light.
61.
State Huygen's
principle of wave theory of light and also use this principle to verify the
laws of reflection of light.
62.
State and use Huygen's
principle of wave theory of light to verify the laws of refraction of light.
63.
State and use Huygen's
principle. Use it to prove Snell's law.
64.
Describe Michelson's
methods for the determine the velocity of light
65.
Describe Foucault's
Method to determination of speed of light.
66.
74. Describe
faccault's experimental method for the measurement of the velocity of light
with necessary theory.
67.
State and explain
Huygen's principle. Use the principle to show that a plane wave incident
obliquery on a plane mirror is reflected as a plane wave so that the
angle of incidence is equal to the angle of reflection.
68.
Describe Michelson's
Method to determination of speed of light. Write advantages of the method over
foucault's method.
69.
State and
explain Huygen's principle. Use the principle to show that a plane wave
front incident obliquely on a plane reflecting surface is reflected as a plane
wave front so that the angle of incidence is equal to the angle of reflection.
70.
State and explain
Huygen's principle. Use the principle to verify the laws of reflection of light
on the basis of wave theory.
71.
Define Huygen's
principle and prove Snell's law by the help of wave theory of light.
72.
Prove the laws of
reflection of light using the wave theory.
73.
State and
explain Huygen's principle. Use the principle to show that a plane wave
front incident obliquely on a plane mirror is reflected as a plane wave
front so that the angle of incidence is equal to the angle of reflection.
74.
A beam of light after
reflection at a plane mirror, rotating 2000 times per minute, passes to a
distant reflector. It returns to the rotating mirror from which it is reflected
to make an angle of 1° with its original direction. If the distance between the
mirrors is 6250m,calculate the velocity of light.
75.
A beam of light
is reflected by a rotating mirror on to a fixed mirror, which sends it
back to the rotating mirror which it is again reflected making an angle of 18°
with its original direction. The distance between the two mirrors is 10 km and
the rotating mirror is making 375 revolutions per second. Calculate the
velocity of light.
76.
A beam of light
is reflected by a rotating mirror on to a fixed mirror, which sends it
back to the rotating mirror which it is again reflected, and then makes an
angle of 18° with its original direction. The distance between the two
mirror is 104m and the rotating mirror is making 375 revolutions per
second. Calculate the velocity of light.
77.
A beam of light
is reflected by a rotating mirror on to a fixed mirror, which sends it
back to the rotating mirror from which it is again reflected and then makes an
angle of 3.6° with the original direction. The distance between the two mirror
is 1km and the rotating mirror is making 750 revs-1. Calculate the
velocity of light.
78.
The radius of
curvature of the curved mirror is 200m and the plane mirror is rotated at 20
revs-1, calculate angle in degree between a ray incident on the
plane mirror and then reflected from it after the light has travelled to the
curved mirror and back to the plane mirror [C=3×108ms-1].
79.
Can a charger particle
move through a magnetic field with out experiencing my force? Explain
80.
Does a chargerd
particle moving through a magnetic field always experience a force? Explain
81.
A current was sent
through a helical coil spring \ the spring contracted, as if it had been
compressed. Why?
82.
If a magnetic force
foes no work charged particles, how can it have any effect on the articles
motion?
83.
Can a charged particle
move through a magnetic field with out experiencing any force? Explain the
reason.
84.
Two straight current
carrying rods are replaced parallel to each other, how can 1(one ) ampere of
current be defined from this arrangement?
85.
An electron beam and a
proton bream are moving parallel to each other is the beginning. Do they always
maintain this status? Justify answer
86.
State Ampere's
circuital theorem.
87.
A current carrying
solenoid tends to contract. Why?
88.
A horizontal wire, of
length 5cm and carrying a current of 2A is placed in the middle of a long
solenoid at right angles to its axis. The solenoid has 100 turns per meter and
carries a steady current . calculate I if the force on the wire is equal to 10-4N(µ0=4π×10-7Hm-1)
89.
A battery of 6V and
internal reistance 0.5Ω is joimned in parallel with another of 10V and internal
resistance 1Ω. The combination sends a current through an external resistance
of 12Ω. Find the current through each battery.
90.
The coil of a moving
coil galvanometer has 50 turns and its resistance is 10Ω. It is replaced by a
coil having 100 turns and resistance 50Ω. Find the factor by which the current
and voltage sensitivities changes.
91.
A horizontal straight
wire, of mass 0.12gm and length 10cm cm is placed perpendicular to uniform
horizontal magnetic field of flux density 0.6T. If the resistance per unit
length of the wire is 3.8Ωm-1,calculate the potential difference
that has to be applied between the end of the wire to make it just self
supporting.
92.
A copper wire has 1029
free electrons per cubic meter, a cross sectional area of 2mm2 and carries a
current of 5 A. Calculate the force acting on each electron if the wore is now
placed in a magnetic field of flux density 0.15 T which is perpendicular to the
wire.
93.
Two long parallel
conductor carry respectively current of 12A and 8A in the same direction. If
the wires are 10 cm apart, find where a third parallel wire also carrying a
current must be placed so that the force experienced it will be zero.
94.
An electron of K.E 10
eV is moving in a circular orbit of radius 11cm in a plane at right angles to a
uniform magnetic field. Determine the value of the flux density. Mass of
electron = 9.1×10-31kg, e=1.6×10-19C
95.
A copper wire has 11029free
electrons per cubic meter and crossectional area 2mm2 carries a current of 6A.
calculate the force acting on each electron if the wire is now placed in
uniform magnetic field of flux density 0.1T perpendicularly.
96.
A slice of
indium antimonide is 2.5mm thick and carries a current of 150mA. A magnetic
field of flux density 0.5T, correctly applied, produces a maximum Hall voltage
of 8.75mV between the edges of the slice. Calculate the density of free charge
carries, assuming they each have a charge of -1.6×10-19C.
97.
A copper wire 28m long
is wound into a flat circular coil 8.0 cm in diameter. If the current of 4.50 A
flows through the coil, what is the magnetic induction at the center?
98.
An alpha particle
makes a full rotation in a circle of radius 1.0 meter in 2.0 sec. calculate the
value of magnetic field induction at the center of the circle.(µ0=4π×10-7Hm-1)
99.
A long wire carrying a
current of 10A is placed perpendicular to magnetic field of flux density 5
Tesla. Calculate the force acting on 2m of the wire.
100.
A stone is dropped
from the top of the tower 300m high splashes into the water of a pond near the
base, of the tower. When is the splash heard at the top? Given that the speed
of sound in air is 340 m/s, g= 9.8 m/s [ ans= 8.70 s]
101.
A stone is
dropped into a well and a splash is heard after 2.6 secs. Calculate the depth
of the well. (Velocity of sound = 334m/s)
102.
When a detonator is
exploded on a railway line, an observer standing on the rail 2km away hears two
sounds. What is the time interval between them? ( Y for steel= 2×1011N/m2,
density of steel= 8000kg/m3, density of air= 1.4 kg/m3 and
atmospheric pressure = 105 N/m2 )
(Ans:- 5.9s)
103.
The interval between
the flash of lightning and the sound of thunder is 2 sec. When the temperature
is 10 oC. How far the stormed if the velocity at 0 oC
is 330m/s. (Ans:- 672m)
104.
A plane progressive
wave is represented by the
equation
a.
y=
0.1sin(200πt-20πx/17) where y and x are in mm and t is in sec, then find i)
frequency ii) wavelength iii) speed iv) phase difference between
two point 0.25m to 1.10 meter from O. v) equation of wave travelling in
opposite direction with double amplitude.
105.
A plane
progressive wave is y = 10–2 Sin (1024t – 25/8 x),
where y is in centimeter, x meter and t in second. Find a) speed of wave, b)
phase difference in radians between the points x = 1.5m and x =
1.66m.
106.
A source of sound of
frequency 550Hz emits waves of wavelength 600mm in air at 20oC. What
will be the wavelength of sound at 0 oC.
(Ans:- 579mm)
107.
A man stationed
between two parallel cliff fires a gun. He hears the first echo after 3sec and
next after 5 sec. What is the distance between two cliffs? Vair=
350m/s) (Ans:- 1400m)
108.
A man standing at one
end of closed corridor 57m long blow a blast of whistle. He found that the time
from the blast to the sixth echo was 2 sec. if the temperature was 17 oC,
what will be the velocity of sound at 0 oC? (Ans;-
331.8m/s)
109.
At what temperature
velocity of sound in air is increased by 50% to that at 27 oC?
110.
Two plane metal plates
4 cm long are held horizontally 3cm part in a vacuum, one being vertically
above the other. The upper plate is at a potential of 300 V and the lower is
earthed. Electrons having a velocity of 1.0x107 ms–1 are
injected horizontally midway between the plates and in a direction parallel to
the plates. Calculate the vertical deflection of the electron beam as it
emerges form the plates. (e/m for electron = 1.8x1011Ckg–1)
( Ans:- 1.44×10-2m)
111.
An oil drop of man 3.25x10–15 kg
falls vertically with uniform velocity, through the air between vertical
parallel plates which are 2cm apart. When a p. d. of 1000V is applied to the
plates the drop moves towards the negatively charge plate, it path being
inclined at 450 to the vertical. Calculate the charge of oil
drop. ) ( Ans:- 6.37×10-19C)
112.
Electron
has velocity 3.52x106 m/s and moves in a circular orbit in
magnetic field 0.2T what will be the radius of the orbit? (Ans:-9.9×10-5m)
113.
An
electron beam passes through a parallel plate capacitor with a velocity
of 107m–1. The length
of each plate is 10cm while the distance between the plates is 5cm. If the
electric intensity between the plates is 20Vcm–1, find the
acceleration and the angle of deflection of the beam. (Given e = 1.6 x 10–19 C
and mass of electron 9.1 x 10–31 kg)
114.
A beam of protons is
accelerated from rest through a potential difference of 2000V and then enters a
uniform magnetic field which is perpendicular to the direction of the proton
beam. If the flux density is 0.2T, calculate the radius of the path which the
beam describes. (proton mass: = 1.7x10–27, electronic charge =
1.6x10–19C)
115.
In a
Miliken-type apparatus the horizontal plate are 1.5 cm apart. With the electric
field switched off an oil drop is observed to fall with the steady velocity
2.5*10-2 cms-1. When the field is switched on the
upper plate being positive, the drop just remains stationary when the potential
different between the plates is 1500V. Calculate the radius of the drop and the
number of electronic charges. (Given- density of oil=900kgm-3 and
viscosity of air=1.8*10-5 NSm2, Neglect air density)
Where are the answer of 96 number numerical probpem? Please help.
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