"OM SAI RAM"
VERNIER CALLIPER
Q.1: What is
vernier calipers?
Ans. It is
simple instrument by which length of an object can be measured accurately up to
one-tenth
of a
millimeter or one-hundredth of a centimeter.
Q.2: What is
the use of Vernier Scale?
Ans. To
increase the accuracy of the main scale.
Q.3: What is
least count (L.C.)?
Ans. The
minimum measurement that can be taken by an instrument.
Q.4: What is
the least count of?
(a) meter
scale (b) Stop Watch (c) Vernier Calliper
Ans. The
least count of:
(a) meter
scale = 0.1 cm or 1 mm.
(b) stop
watch = 0.01 sec or 1/100 sec. or according to stop watch.
(c) vernier
scale = 0.01 cm or 0.1 mm
Q.5: What
are units of vernier scale?
Ans. Vernier
has not units of its own.
Q.6: What is
the difference in the measurement of one smaller division on the main scale
(M.S.) and
that of
vernier scale (V.S.)
Ans. (1
smallest Div. on M.S.) – (1 smallest Div. on V.S) = 0.1 – 0.09 = 0.01 cm
= Least
count.
Q.7: How the
L.C. of a vernier is determined?
Ans. By
using the relation:
L.C. = Smallest
division on Main scale
Total number of divisions on vernier
Q.8: Will
the accuracy of a vernier will increase or decrease if 20 divisions are made in
the same
length?
Ans. The
accuracy will increase since the L.C. will decrease i.e.
Accuracy α 1
Least count
Q.9: Which one is smaller M.S. div. or V.S. div.?
Ans. V.S. division.
Q.10: 1 division on V.S. = _____ cm.
Ans. 0.09 cm.
10 div. on V.S. = 0.9 cm
1 div. on V.S. = 0.9/10 cm = 0.09 cm
Q.11: What are the functions of
(a) Sliding strip (b) Upper jaws
Ans. (a) For measuring depth. (b) For measuring the inner diameter.
Q.12: What is meant by zero error (Z.E.)?
Ans. The error which arises when zeros of M.S. and V.S. do not coincide
upon joining the two jaws.
Q.13: When Z.E. is positive?
Ans. The Z.E. is positive when the zero of V.S. is to the right of the
zero of M.S.
Q.14: How we find the corrected reading?
Ans. Corrected reading = Meaning reading – ( + Z.E.)
Q.15: Do you know any use of vernier scale?
Ans. It is used in spectrometer, barometer, traveling microscope, etc.
Q.16: What are significant figures?
Ans. Numbers 0, 1, 2, 3, ……. are called significant figures when they
occur. The zero is not a
significant figure if it is at the extreme left or extreme right of a
number, e.g.
1.02 has three significant figures, but 1.20 has two significant
figures.
Q.17: What is meant by degree of accuracy?
Ans. It is the measurement estimated by the number of significant
figures in the result.
Q.18: Why is the vernier calipers so called?
Ans. A French mathematician named Pierre Vernier invented it and it is
named after him.
Q.19: How does temperature affect the length of a cylinder?
Ans. The length of a cylinder increases with the increase of temperature
and decreases with the
decrease of temperature.
Q.20: What is the unit of volume?
Ans. In MKS system, the unit of volume is m3. In CGS system, the unit
of volume is cm3. In FPS
system, the unit of volume is ft3.
SCREW GAUGE
Q.1: What is a screw?
Ans. Screw is a simple machine related to inclined plane.
Q.2: What is meant by “gauge”?
Ans. The gauge means device or instrument.
Q.3: Name two main parts of a screw-gauge?
Ans. (a) A nut (b) A bolt or screw
Q.4: What is meant by pitch of a screw?
Ans. Pitch is the distance between two nearest (consecutive or
successive) threads along the axis of
screw.
Q.5: How is the pitch found?
Ans. By dividing the distance covered by the screw in a known number of
rotations by the total
number of relations.
Q.6: What is the least count (L.C.) of the screw gauge?
Ans. L.C. of screw gauge = 0.001 cm.
Q.7: How the L.C. of a screw gauge is found?
Ans. By using the relation
L.C. = Pitch of the screw .
No. of circular scale
divisions
Q.8: What is meant by zero error of a screw-gauge?
Ans. The error which arises when the zero of circular scale does not
coincide with the zero of the
main scale upon joining the two studs.
Q.9: When the zero-error is positive?
Ans. If the zero of the circular scale lies above the reference line,
provided that the fixed and
movable studs are in contact.
Q.10: What is the degree of accuracy of the screw gauge?
Ans. Degree of accuracy = L.C. or
Reading power = 0.001 cm
Q.11: What is mechanical advantage of a screw gauge?
Ans. Like a screw jack mechanical advantage of a screw gauge is 2π r/h;
where ‘r’ is the radius of
cylinder of the screw and ‘h’ is the pitch.
Q.12: What is meant by range of the screw gauge?
Ans. The maximum length of the main scale.
Q.13: What is formula for area of cross section of wire?
Ans. Area of circle = 2 π r
Q.14: What is back lash error?
Ans. Within a nut there is a little space for the play of screw. Due to
continuous use this space
increases. Thus when the screw is turned in one direction the stud
moves as usual. However,
when the screw is rotated in the opposite direction, the stud does not
move for a while. This
error is called Back lash error. In short
“Back lash error is the error introduced on reversing the direction of
rotation”.
Q.15: How back lash error is avoided?
Ans. By turning the screw in one direction only.
Q.16: What are “precision instrument”?
Ans. The instrument that can measure up to a fraction of a mm, e.g.,
vernier caliper, screw gauge
and spherometer.
Q.17: What is Pi (π)?
Ratio between the circumference of a circle to its diameter.
π = Length of Circumference
ndiameter
Q.18: Does the diameter of the screw depend on temperature?
Ans. Yes it does. Diameter increases with the increase of temperature
and decreases with the
decrease of temperature
SPHEROMETER
Q.1: Why the instrument is given the name “spherometer”?
Ans. Because it is used to determine the radius of curvature of a
spherical surface.
Q.2: What is the pitch of a spherometer?
Ans. The distance covered by the circular disc in one complete rotation
along the main scale. Mostly
pitch of spherometer = 1 mm = 0.1 cm.
Q.3: How do you find the least count of spherometer?
Ans. L.C. of spherometer = Pitch of screw
No. of divisions an circular scale
= 0.1 cm
100
= 0.001 cm.
Q.4: What is meant by ‘radius of curvature’ of a surface?
Ans. The radius of that sphere from which the surface is cut.
Q.5: What is the radius of curvature of phone surface?
Ans. Infinite.
Q.6: What is the formula for the radius of curvature?
Ans. R = a2 + h
6h 2
Where,
a = mean distance between the legs of the spherometer, and
h = height or depth of a surface
Q.7: Is there any zero error in a spherometer?
Ans. Spherometer may have a zero error.
Z.E. in spherometer = reading on the plane glass sheet
Q.8: When the zero error (Z.E.) is positive and when negative?
Ans. Positive: If the edge of the circular disc is at zero of main
scale and the zero of the circular
scale is ahead of the edge of main scale. If it is behind the edge of
main scale, the Z.E. is
negative.
Q.9: Can you measure the radius of curvature of wrist-watch glass by
using a spherometer?
Ans. No, because the wrist-watch glass is small and all the legs of the
spherometer cannot rest on it.
Q.10: What will be the effect of:
(a) changing the pitch or
(b) changing the number of circular divisions upon accuracy or least
count.
Ans. (a) If we decrease the pitch the L.C. will decrease and hence the
accuracy increases.
(b) If we increase the No. of circular divisions, the accuracy
increases since the L.C. decreases.
Q.11: What are the other uses of spherometer?
Ans. (a) In finding a small increase in length during finding the
coefficient of linear expansion.
(b) In finding the small change in length due to the change in the
weight suspended during the
determination of young’s modules.
Q.12: Why main scale is marked on both sides of zero?
Ans. To measure both height and depth.
Q.13: Is paper insertion method for testing the touching position of
the screw is correct?
Ans. No, because the thickness of ordinary paper (0.01 cm) is greater
than the L.C.
Q.14: Define focal length?
Ans. The distance between the pole and the principal focus of spherical
mirror is called the focal
length. The focal length of spherical mirror is half of its radius of
curvature.
Hooke’s Law
Q.1: Define elasticity.
Ans. Property of materials to regain their original length, volume or
shape after the deforming force
has been removed.
Q.2: State Hooke’s Law.
Ans. “If the deforming force is not greater than elastic limit, the
strain is directly proportional to the
stress.”
Stress α Strain
or Stress = E
Strain
Here constant ‘E’ is called “MODULUS OF ELASTICIT”.
Q.3: Define YOUNG’S MODULUS(Y).
Ans. The ratio of longitudinal stress to the linear strain
Longitudinal Stress = Y
Linear Strain
Q.4: What is elastic limited?
Ans. The maximum value of stress beyond which stress is not
proportional to strain. (Beyond elastic
limit strain is rapid).
Q.5: Define STRESS.
Ans. The restoring force per unit area set up inside the body which is
under the influence of
deforming force.
Stress (inside the body) = deforming force (externally applied)
Q.6: Define Strain.
Ans. The ratio of change in length (L), volume (V) or shape to the
original length (L) volume (V) or
shape.
Q.7: What are the units of:
(a) Stress (b) Strain (c) Young’s modulus
Ans. (a) Newton / meter2 or dynes / cm2
(b) No units since if the ratio between the similar quantities
(c) N / m2 or dynes / cm2
Q.8: What is the function of second wire?
Ans. To eliminate the error due to change in temperature.
Q.9: Which one is more elastic, foam or iron?
Ans. Iron, because iron can regain its original shape or length more
easily than foam.
Q.10: Gases and liquids have elasticity or not?
Ans. Yes, they have.
Pendulum Experiment
Q.1:
Define simple pendulum.
Ans.
An ideal simple pendulum is defined as ‘single isolated particle suspended by a
weightless,
flexible
and inextensible string with a friction-less support’.
Q.2:
Why the word ‘SIMPLE’ is used before the pendulum?
Ans.
Because the pendulums used in the wall clocks are ‘COMPOUND PENDULUMS’, in
which a metallic rod is used in place of the thread.
Q.3:
Define ‘g’?
Ans.
Acceleration due to gravity.
Q.4:
What is the difference between ‘g’ and ‘G’?
Ans.
The value of G (gravitational constant) remains constant throughout the
universe, whereas the value of ‘g’ decreases with the increase in the height.
Q.5:
What is the value of ‘g’ at the C.G. of the earth?
Ans.
Zero.
Q.6:
How the value of ‘g’ changes as we move from the surface towards the C.G. of
the earth?
Ans.
As a rule it should decrease gradually but due to variable density of the
earth, it increases up to a small depth and then decreases.
Q.7:
Where the ‘g’ is greater, at equator or poles?
Ans.
At the poles (where the earth is slightly compressed).
Q.8:
Where ‘g’ will be smaller, at Karachi or at Muree?
Ans.
At Muree (7000 ft. above sea level).
Q.9:
What is the value of ‘g’ at sea level?
Ans.
g = 9.781 m/s2 at equator.
g
= 9.832 m/s2 at poles.
Q.10:
Why the amplitude of the pendulum is kept small (2cm or about 5 cm)?
Ans.
If the amplitude is large the motion of the simple pendulum will not be simple
harmonic. If θ will not be small Sinθ ≠ θ and T ≠ 2 √L/g.
Q.11:
Define simple harmonic motion (S.H.M).
Ans.
The motion of the vibrating body is S.H.M. when
(a)
The magnitude of its acceleration is directly proportional to the displacement
x from the
mean
position.
(b)
The direction of acceleration is always towards the mean position (that is
opposite to x)
mathematically:
a
α - x
Q.12:
Define vibratory system?
Ans.
Back and forth or to and from motion between two fixed positions.
Q.13:
Define the following terms:
(a)
amplitude (xo) (b) oscillation or vibration
(c)
frequency (f) (d) time period (T)
Ans.
(a) Amplitude: the maximum displacement from the mean (equilibrium) position.
(b)
Oscillation: the motion from one extreme position to the other and then back to
the
original
one.
(c)
Frequency: number of vibrations per second.
(d)
time period: time taken for one vibration.
Q.14:
What is the relation between frequency and time period?
Ans.
f = 1/T
Q.15:
What are the units of frequency?
Ans.
Vibrations / sec, cycles / sec (c.p.s.) or Hertz.
Q.16:
What is the frequency of a second pendulum?
Ans.
0.5 Hz or 1 Hz, because
f
= 1 = 1 ( T = 2 s for a second’s pendulum)
T
2
Q.17:
Prove that g = 4 π2 /LT2
Ans.
For a simple pendulum time period is given by:
T
= 2 π √L/g
T2
= 4 π2 L/g
i.e.
g = 4 π2 L/T2
Where
L = length of the simple pendulum.
Q.18:
Let the time period of a simple pendulum is 4s at the place where g = 900 cm/s2.
What will be
the
time period at the place where g = 100 cm/s2.
Ans.
12 s.
EXPLANATION:
g = 4 π2 L/T2 => T2 α 1 when L remain constant G
Therefore,
when g decreases by 9 times, the ‘T’ increases by 3 times.
Q.19:
Time period will increase or decrease if we use a heavier bob.
Ans.
There will be no change in the time period.
EXPLANATION:
The relation T = 2 √L/g shows that there is no effect of mass on the
time
period.
Q.20:
Can you replace the thread by a metallic wire?
Ans.
No, because the wire is not flexible.
EXPLANATION:
By definition of simple pendulum, the string must be perfectly flexible. The
thread
is flexible but a metallic wire is not. That is why the wire can be used in
place of thread.
Q.21:
What is restoring force?
Ans.
The force which tends to bring a vibrating body towards the mean position.
Q.22:
What is restoring force (net force) acting on the bob?
Ans.
If the air friction is neglected, restoring force on the bob = mg Sin θ.
Q.23:
What is net force on the bob, at equilibrium (mean) position?
Ans.
Zero, since at mean position the weight of the bob is perfectly balanced by the
tension (T) in the string.
Q.24:
Define equilibrium.
Ans.
A body is said to be in equilibrium when its linear and angular accelerations
are zero or when F = 0 &
EXPLANATION:
when a body is
(a)
at rest or
(b)
moving with uniform linear velocity its linear acceleration is zero.
(c)
not rotating at all or
(d)
rotating at a constant rate it is in equilibrium.
Q.25:
Can you replace the thread by a rubber band?
Ans.
No, because it is not inextensible. By definition the string must be
inextensible.
Q.26:
Can we use a cricket ball in place of the bob?
Ans.
No, by definition of simple pendulum the bob must be as small as possible.
18
Prepared by: Muhammad Hassam
Q.27:
Why the pendulum stops after some time?
Ans.
Its energy is lost as heat.
Q.28:
How P.E. and K.E. of the pendulum interchange into each other during
vibrations?
Ans.
(a) In the form of P.E. at extreme positions.
(b)
In the form of K.E. at mean position and
Spectrum Classes By Er.Shyam Pachori CL 157 D.D Nagar 9039803981
