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Cds Journey > Physics > Flashcards

Physics Flashcards

1
Q

A car undergoes a uniform circular motion. The acceleration of the car is

A

non-zero but not a constant

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2
Q

Total energy consumed by the electric device

A

Power × Duration

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3
Q

Rutherford’sα-particlescattering experiment on thin gold foil was responsible for the discovery of

A

atomic nucleus

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4
Q

Magnification is

A

observed size of specimen/actual
size

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5
Q

Rate of evaporation increases with

A

Increase in surface area
Increase in temperature
Increase is wind speed
Decrease in humidity
Decrease in Pressure

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6
Q

If an object is at rest, then the time (X-axis) versus distance (Y-axis) graph

A

is horizontal

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7
Q

If the speed of a moving magnet inside a coil increases, the electric current in the coil

A

increases

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8
Q

The frequency (in Hz) of a note that is one octave higher than 500 Hz is

A

1000

An octave or perfect octave is the interval between one musical pitch and another with double its frequency

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9
Q

Soapsolutionusedforcleaning purpose appears cloudy. This is due to the fact that soap micelles can

A

scatter light

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10
Q

Peopleprefertowearcotton clothes in summer season. This is due to the fact that cotton clothes are

A

good absorbers of water

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11
Q

Twoidenticalsolidpieces,oneof gold and other of silver, when immersed completely in water exhibit equal weights. When weighed in air (given that, density of gold is greater than that of silver),

A

Both silver and gold pieces weigh
equal

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12
Q

Anelectronandaprotonstarting from rest get accelerated through potential difference of 100 kV. The final speeds of the electron and the proton are ve and vp, respectively. Who has higher speed.

A

Here, we can see that mass of proton is very high than mass of electron

so velocity of electronis more than proton

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13
Q

If two vectors A and B are at an angle θ ≠ 0 °, then

A

|A|+|B|>|A +B|

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14
Q

The Hooke’s law is valid for

A

Hooke’s law is valid for only proportional region of the stress- strain curve.

Hooke’s law → stress ∝ strain

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15
Q

If two miscible liquids of same volume but different densities ρ1 and ρ2 are mixed, then the density of the mixture is given by

A

2(p1)(p2) / p1 + p2

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16
Q

The visible portion of the electromagnetic spectrum is

A

light

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17
Q

When a convex lens produces a real image of an object, the minimum distance between the object and image is equal to

A

four times the focal length of the
convex lens

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18
Q

The direction of magnetic field at any location on the earth’s surface is commonly specified in terms of

A

horizontal component of the field

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19
Q

Acircuithasafusehavinga rating of 5 A. What is the maximum number of
100 W-220 V bulbs that can be safely connected in parallel in the circuit?

A

11

Potential difference, V = 220 V

P = VI

100 × x = 220 × 5

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20
Q

Define Convection

A

Convection is the process of heat transfer of the bulk movement of molecules within fluids such as gases and liquids.

In this process, the heat transfers is by the actual motion of matter. It happens in liquid and gases.

Boiling water, land and sea breeze, circulation of air around blast furnace, etc., are the example of convection.

21
Q

____ represents a relation for ‘heat lost = heat gained’

A

Principle of calorimetry

22
Q

Thepressureofafluidvaries
withdepthhasp=p +ρgh, 0
where ρ is the fluid density. This expression is associated
with

A

Pascal’s law

i.e. Pressure of fluid varies with depth h
can expressed

23
Q

Why is argon gas used along with
tungsten wire in an electric bulb?

A

Argon being an inert gas used in electric bulb to increase the life of the bulb. It prevents the tungsten filaments from descend too quickly.

24
Q

Whichoneofthefollowingisthe correct relation between the Kelvin temperature T and the Celsius temperature t ?

A

T=tC+273.15

25
Q

Soundwavescannottravel
through a

A

vacuum.

26
Q

Which one of the following is the
value of 1 nanometre?

A

10−7 cm

27
Q

______ energy is the energy possessed by an object due to its motion.

A

Kinetic

28
Q

only _____ energy of an object cannot be conserved but the sum of _____ and potential energies is conserved.

A

kinetic

29
Q

Working of safety fuses depends upon

A

Working of safety fuses depends upon magnitude of the current and heating effect of the current.

30
Q

Resistance of wire,

A

R = ρ l/A

31
Q

Arayoflightisincidentona plane mirror at an angle of 40° with respect to surface normal. When it gets reflected from the mirror, it undergoes a deviation of

A

100°

deviation =
δ = 180° − 2∠i
= 180° − 2 × 40°
= 180° − 80° = 100°

32
Q

After using for some time,big transformers get heated up. This is due to the fact that

A

(i) The current flowing through the wire of resistance (R ) produces a heat (I2R ).

(ii) The magnetisation of the core
produces heat due to hysteresis
loss.

33
Q

Joule-Thomsonprocessis extremely useful and economical for attaining low temperature. The process can be categorised as

A

In Joule-Thomson process, the temperature remains low. Thus, heat content of the process can be taken as constant. Therefore, the process can be categorised as adiabatic process.

34
Q

Ultrasonicwavesareproducedby making use of

A

Piezoelectric effect is used in the production of ultrasonic sound waves. Therefore, piezoelectric material, i.e. compound of sodium or potassium can be utilised for the production of ultrasonic waves.

35
Q

Define chain reaction

A

Chain reaction is the principle of nuclear reactors, while uncontrolled chain reaction is the principle of atom bomb.

36
Q

In nuclear reactor, the reaction is controlled by control material like as _________.

A

cadmium rod or moderator

37
Q

Whenapieceofpuresiliconis
doped with aluminium, then

A

the doped silicon piece will become p-type

This type of semiconductor, hence formed by doping of trivalent impurity atoms, i.e. Al is known as p-type semiconductor.

38
Q

SupposevoltageVisapplied across a resistance R. The power dissipated in the resistance is P. Now, the same voltage V is applied across a parallel combination of three equal resistors each of resistance R. Then, the power dissipated in the second case will be

A

3P

For parallel combinations,
1/Req =1/R+1/R+1/R=3/R
Req =R/3

Power (P) = V2 / R

39
Q

In total internal reflection, the
light travels from

A

denser to rarer medium and it occurs with loss of intensity

In total internal reflection, light travels from an optically denser medium to a rarer medium at the interface. It is partly reflected back into the same medium and partly refracted back to the second medium. The intensity of the reflected and refracted rays do not remain constant but reflection occurs with loss of intensity.

40
Q

Thespringconstantofaspring depends on its

A

thickness, its diameter and its material

41
Q

The pressure exerted by a
760 mm column of mercury at 0°C is known as

A

1 atm

42
Q

The sensitivity of the human ear depends upon the frequency of sound. It is most sensitive in the frequency range ______

A

20Hz to 20000Hz

43
Q

The rate of change of momentum of a body is equal to the resultant

A

force

44
Q

The SI unit of mechanical energy is

A

joule

45
Q

Two systems are said to be in thermal equilibrium, if and only if

A

there is no heat flow between them

46
Q

The velocity of sound depends upon the nature of ______.

A

medium

47
Q

A myopic person has a power of − 1.25 D. What is the focal length and nature of his lens?

A

− 80 cm and concave lens

Power of lense = 1/f

f = -4/5m = -80cm

48
Q

The focal length of the lens of a normal human eye

A

2.5 cm

49
Q

Newton’s laws of motion do not hold good for objects

A

moving with velocity comparable to
velocity of light

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