12583 + Mcqs in Physics Page 25 McqOptions

1201.	If the K.E. of a body is increased by 300%, its momentum will increase by [JIPMER 1978; AFMC 1993; RPET 1999; CBSE PMT 2002]
A.	100%
B.	150%
C.	\[\sqrt{300}%\]
D.	175%
Answer» B. 150%

Discussion

1202.	A simple pendulum of length l has a brass bob attached at its lower end. Its period is T. If a steel bob of same size, having density x times that of brass, replaces the brass bob and its length is changed so that period becomes 2T, then new length is [MP PMT 2002]
A.	2 l
B.	4 l
C.	4 l x
D.	\[\frac{4l}{x}\]
Answer» C. 4 l x

Discussion

1203.	In a seconds pendulum, mass of bob is 30 gm. If it is replaced by 90 gm mass. Then its time period will [Orissa PMT 2001]
A.	1 sec
B.	2 sec
C.	4 sec
D.	3 sec
Answer» C. 4 sec

Discussion

1204.	A plate oscillated with time period ?T?. Suddenly, another plate put on the first plate, then time period [AIEEE 2002]
A.	Will decrease
B.	Will increase
C.	Will be same
D.	None of these
Answer» D. None of these

Discussion

1205.	DIRECTION: Read the passage given below and answer the questions that follows: A diathermic piston divides adiabatic cylinder volume \[{{V}_{0}}\] into two equal parts as shown in the figure. Both parts contains ideal monoatomic gases. The initial pressure and temperature of gas in left compartment are \[{{P}_{0}}\] and v while that in right compartment are \[2{{P}_{0}}\] and \[2{{T}_{0}}\]. Initially the piston is kept fixed and the system is allowed acquire a state of thermal equilibrium. The pressure in left compartment after thermal equilibrium is achieved is
A.	\[{{P}_{0}}\]
B.	\[\frac{3}{2}{{P}_{0}}\]
C.	\[\frac{4}{3}{{P}_{0}}\]
D.	None of these
Answer» C. \[\frac{4}{3}{{P}_{0}}\]

Discussion

1206.	Which of the following statements are true regarding Bohr's model of hydrogen atom (I) Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus (II) Radii of allowed orbits of electron are proportional to the principal quantum number (III) Frequency with which electrons orbits around the nucleus in discrete orbits is inversely proportional to the principal quantum number (IV) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits Select correct answer using the codes given below Codes :
A.	I and III
B.	II and IV
C.	I, II and III
D.	II, III and IV
Answer» B. II and IV

Discussion

1207.	What will be the angular momentum of a electron, if energy of this electron in H-atom is 1.5eV (in J-sec)
A.	\[1.05\times {{10}^{-34}}\]
B.	\[2.1\times {{10}^{-34}}\]
C.	\[3.15\times {{10}^{-34}}\]
D.	\[-2.1\times {{10}^{-34}}\]
Answer» D. \[-2.1\times {{10}^{-34}}\]

Discussion

1208.	A body of mass m kg is lifted by a man to a height of one metre in 30 sec. Another man lifts the same mass to the same height in 60 sec. The work done by them are in the ratio [MP PMT 1993]
A.	\[1:2\]
B.	1 : 1
C.	2 : 1
D.	4 : 1
Answer» C. 2 : 1

Discussion

1209.	The velocity of waves in a string fixed at both ends is 2 m/s. The string forms standing waves with nodes 5.0 cm apart. The frequency of vibration of the string in Hz is [SCRA 1998]
A.	40
B.	30
C.	20
D.	10
Answer» D. 10

Discussion

1210.	Which of the following is the example of transverse wave [CPMT 1999]
A.	Sound waves
B.	Compressional waves in a spring
C.	Vibration of string
D.	All of these
Answer» D. All of these

Discussion

1211.	Standing waves are produced in a 10 m long stretched string. If the string vibrates in 5 segments and the wave velocity is 20 m/s, the frequency is [CBSE PMT 1997; AIIMS 1998; JIPMER 2000]
A.	2 Hz
B.	4 Hz
C.	5 Hz
D.	10 Hz
Answer» D. 10 Hz

Discussion

1212.	The electrochemical equivalent of magnesium is \[0.126\,mg/C\]. A current of 5 A is passed in a suitable solution for 1 hour. The mass of magnesium deposited will be [MP PMT 1995]
A.	0.0378 gm
B.	0.227 gm
C.	0.378 gm
D.	2.27 gm
Answer» E.

Discussion

1213.	DIRECTION: Read the passage given below and answer the questions that follows: A diathermic piston divides adiabatic cylinder volume \[{{V}_{0}}\] into two equal parts as shown in the figure. Both parts contains ideal monoatomic gases. The initial pressure and temperature of gas in left compartment are \[{{P}_{0}}\] and v while that in right compartment are \[2{{P}_{0}}\] and \[2{{T}_{0}}\]. Initially the piston is kept fixed and the system is allowed acquire a state of thermal equilibrium. If the pin which was keeping the piston fixed is removed and the piston is allowed to slide slowly such that a state of mechanical equilibrium is achieved. The volume of left compartment when piston is in equilibrium is
A.	\[\frac{3}{4}{{V}_{0}}\]
B.	\[\frac{{{V}_{0}}}{4}\]
C.	\[\frac{{{V}_{0}}}{2}\]
D.	\[\frac{2}{3}{{V}_{0}}\]
Answer» D. \[\frac{2}{3}{{V}_{0}}\]

Discussion

1214.	DIRECTION: Read the passage given below and answer the questions that follows: A diathermic piston divides adiabatic cylinder volume \[{{V}_{0}}\] into two equal parts as shown in the figure. Both parts contains ideal monoatomic gases. The initial pressure and temperature of gas in left compartment are \[{{P}_{0}}\] and v while that in right compartment are \[2{{P}_{0}}\] and \[2{{T}_{0}}\]. Initially the piston is kept fixed and the system is allowed acquire a state of thermal equilibrium. The heat that flown from right compartment to left compartment before thermal equilibrium is achieved is
A.	\[{{P}_{0}}{{V}_{0}}\]
B.	\[\frac{3}{4}{{P}_{0}}{{V}_{0}}\]
C.	\[\frac{3}{8}{{P}_{0}}{{V}_{0}}\]
D.	\[\frac{2}{3}{{P}_{0}}{{V}_{0}}\]
Answer» D. \[\frac{2}{3}{{P}_{0}}{{V}_{0}}\]

Discussion

1215.	Assertion : The graph of total energy of a particle in SHM w.r.t., position is a straight line with zero slope. Reason : Total energy of particle in SHM remains constant throughout its motion.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

1216.	Assertion : An artificial satellite with a metal surface is moving above the earth in a circular orbit. A current will be induced in satellite if the plane of the orbit is inclined to the plane of the equator. Reason : The current will be induced only when the speed of satellite is more than 8 km/sec.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

1217.	Infinite springs with force constant k, 2k, 4k and 8k.... respectively are connected in series. The effective force constant of the spring will be [J & K CET 2004]
A.	2K
B.	k
C.	k/2
D.	2048
Answer» D. 2048

Discussion

1218.	Two springs of constant \[{{k}_{1}}\]and \[{{k}_{2}}\]are joined in series. The effective spring constant of the combination is given by [CBSE PMT 2004]
A.	\[\sqrt{{{k}_{1}}{{k}_{2}}}\]
B.	\[({{k}_{1}}+{{k}_{2}})/2\]
C.	\[{{k}_{1}}+{{k}_{2}}\]
D.	\[{{k}_{1}}{{k}_{2}}/({{k}_{1}}+{{k}_{2}})\]
Answer» E.

Discussion

1219.	A particle at the end of a spring executes simple harmonic motion with a period \[{{t}_{1}}\], while the corresponding period for another spring is \[{{t}_{2}}\]. If the period of oscillation with the two springs in series is T, then [AIEEE 2004]
A.	\[T={{t}_{1}}+{{t}_{2}}\]
B.	\[{{T}^{2}}=t_{1}^{2}+t_{2}^{2}\]
C.	\[{{T}^{-1}}=t_{1}^{-1}+t_{2}^{-1}\]
D.	\[{{T}^{-2}}=t_{1}^{-2}+t_{2}^{-2}\]
Answer» C. \[{{T}^{-1}}=t_{1}^{-1}+t_{2}^{-1}\]

Discussion

1220.	The shortest wavelength in the Lyman series of hydrogen spectrum is 912 Å corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is about [MP PMT 2004]
A.	3648 Å
B.	8208 Å
C.	1228 Å
D.	6566 Å
Answer» B. 8208 Å

Discussion

1221.	The moment of inertia of a thin uniform rod of mass M and length L about an axis passing through its midpoint and perpendicular to its length is\[{{I}_{0}}\]. Its moment of inertia about an axis passing through one of its ends and perpendicular to its length is
A.	\[{{I}_{0}}+M{{L}^{2}}/2\]
B.	\[{{I}_{0}}+M{{L}^{2}}/4\]
C.	\[{{I}_{0}}+2M{{L}^{2}}\]
D.	\[{{I}_{0}}+M{{L}^{2}}\]
Answer» C. \[{{I}_{0}}+2M{{L}^{2}}\]

Discussion

1222.	In the arrangement shown in the figure. The mass of wedge A and that of the block B are 3m and in respectively. Friction exists between A and B only. The mass of the block C is m.The force F = 19.5 m x g is applied on the block C as shown in the figure. The minimum coefficient of friction (\[\mu \]) between A and B so that B remains stationary with respect to wedge A will be
A.	\[\frac{2}{3}\]
B.	\[\frac{1}{10}\]
C.	\[\frac{2}{5}\]
D.	\[\frac{1}{4}\]
Answer» E.

Discussion

1223.	A worker piles up sand onto a circular area of radius R. No sand is to spill onto the surrounding area. The coefficient of friction of sand on sand is \[\mu \]. The greatest volume of the sand that can be stored in the manner is
A.	\[\frac{\pi \mu {{R}^{3}}}{3}\]
B.	\[\frac{\pi \mu {{R}^{3}}}{6}\]
C.	\[\frac{\pi {{R}^{3}}}{3\mu }\]
D.	None
Answer» B. \[\frac{\pi \mu {{R}^{3}}}{6}\]

Discussion

1224.	A wire of cross section 4 mm2 is stretched by 0.1 mm by a certain weight. How far (length) will be wire of same material and length but of area 8 mm2 stretch under the action of same force [Kerala PMT 2004]
A.	0.05 mm
B.	0.10 mm
C.	0.15 mm
D.	0.20 mm
E.	0.25 mm
Answer» B. 0.10 mm

Discussion

1225.	Particle nature and wave nature of electromagnetic waves and electrons can be shown by
A.	Electron has small mass, deflected by the metal sheet
B.	X-ray is diffracted, reflected by thick metal sheet
C.	Light is refracted and defracted
D.	Photoelectricity and electron microscopy
Answer» E.

Discussion

1226.	Which of the following is constructed on the principle of electromagnetic induction [MP PMT 2002]
A.	Galvanometer
B.	Electric motor
C.	Generator
D.	Voltmeter
Answer» D. Voltmeter

Discussion

1227.	In figure find the total magnification after two successive reflections first on \[{{M}_{1}}\] and then on \[{{M}_{2}}.\]
A.	+1
B.	-2
C.	+2
D.	-1
Answer» D. -1

Discussion

1228.	A series ac circuit consist of an inductor and a capacitor. The inductance and capacitance is respectively 1 henry and \[25\mu F.\] If the current is maximum in circuit then angular frequency will be [RPMT 1999]
A.	200
B.	100
C.	50
D.	200/2\[\pi \]
Answer» B. 100

Discussion

1229.	Nuclear fission was discovered by
A.	Auto Hahn and F. strassmann
B.	Fermi
C.	Bethe
D.	Rutherford
Answer» B. Fermi

Discussion

1230.	In the following reaction the value of X is \[_{7}{{N}^{14}}{{+}_{2}}H{{e}^{4}}\,\to \,X{{+}_{1}}{{H}^{1}}\]
A.	\[_{8}{{N}^{17}}\]
B.	\[_{8}{{O}^{17}}\]
C.	\[_{7}{{O}^{16}}\]
D.	\[_{7}{{N}^{16}}\]
Answer» C. \[_{7}{{O}^{16}}\]

Discussion

1231.	?Stem Correction? in platinum resistance thermometers are eliminated by the use of [AIIMS 1998]
A.	Cells
B.	Electrodes
C.	Compensating leads
D.	None of the above
Answer» D. None of the above

Discussion

1232.	Unit of stress is [MP PMT 1984]
A.	\[N/m\]
B.	\[N-m\]
C.	\[N/{{m}^{2}}\]
D.	\[N-{{m}^{2}}\]
Answer» D. \[N-{{m}^{2}}\]

Discussion

1233.	Assertion : It is essential that all the lines available in the emission spectrum will also be available in the absorption spectrum. Reason : The spectrum of hydrogen atom is only absorption spectrum.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» E. If assertion is false but reason is true.

Discussion

1234.	The angle of polarisation for any medium is \[60{}^\circ \]The critical angle for this is
A.	\[{{\sin }^{-1}}\frac{1}{\sqrt{3}}\]
B.	\[{{\cos }^{-1}}\sqrt{3}\]
C.	\[{{\sin }^{-1}}\sqrt{3}\]
D.	\[{{\tan }^{-1}}\sqrt{3}\]
Answer» B. \[{{\cos }^{-1}}\sqrt{3}\]

Discussion

1235.	A body is executing S.H.M. When its displacement from the mean position are 4 cm and 5 cm, it has velocities \[10cm\,{{s}^{-1}}\] and \[8\,cm\,{{s}^{-1}}\] respectively. Its periodic time is
A.	\[\pi /2\,s\]
B.	\[\pi s\]
C.	\[3\pi /2s\]
D.	\[2\pi s\]
Answer» C. \[3\pi /2s\]

Discussion

1236.	If a simple harmonic oscillator has got a displacement of 0.02 m and acceleration equal to \[2.0m{{s}^{-2}}\] at any time, the angular frequency of the oscillator is equal to [CBSE PMT 1992; RPMT 1996]
A.	\[10\,rad\,{{s}^{-1}}\]
B.	\[0.1\,rad\,{{s}^{-1}}\]
C.	\[100\,rad\,{{s}^{-1}}\]
D.	\[1\,rad\,{{s}^{-1}}\]
Answer» B. \[0.1\,rad\,{{s}^{-1}}\]

Discussion

1237.	To make the frequency double of an oscillator, we have to [CPMT 1999]
A.	Double the mass
B.	Half the mass
C.	Quadruple the mass
D.	Reduce the mass to one-fourth
Answer» E.

Discussion

1238.	What is constant in S.H.M. [UPSEAT 1999]
A.	Restoring force
B.	Kinetic energy
C.	Potential energy
D.	Periodic time
Answer» E.

Discussion

1239.	In Bohr?s model, if the atomic radius of the first orbit is \[{{r}_{0}}\], then the radius of the fourth orbit is [CBSE PMT 2000]
A.	\[{{r}_{0}}\]
B.	\[4{{r}_{0}}\]
C.	\[{{r}_{0}}/16\]
D.	\[16{{r}_{0}}\]
Answer» E.

Discussion

1240.	Mercury thermometers can be used to measure temperatures upto [CBSE PMT 1992, 96; BHU 1998; UPSEAT 1998]
A.	100°C
B.	212°C
C.	360°C
D.	500°C
Answer» D. 500°C

Discussion

1241.	A transformer is employed to reduce 220 V to 11 V. The primary draws a current of 5 A and the secondary 90 A. The efficiency of the transformer is [MP PMT 1992, 2001, 04]
A.	20%
B.	40%
C.	70%
D.	90%
Answer» E.

Discussion

1242.	Assertion : The percentage change in time period is 1.5%, if the length of simple pendulum increases by 3%. Reason : Time period is directly proportional to length of pendulum.
A.	If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.	If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.	If assertion is true but reason is false.
D.	If the assertion and reason both are false.
E.	If assertion is false but reason is true.
Answer» D. If the assertion and reason both are false.

Discussion

1243.	If a rod is in variable state (not in steady state), then
A.	temperature gradient remains constant
B.	temperature of rod is changing with distance from one end and with time also
C.	temperature of rod is not depending on time
D.	temperature of rod is not depending on distance from one end
Answer» C. temperature of rod is not depending on time

Discussion

1244.	A body cools down from \[{{70}^{o}}C\] to \[{{60}^{o}}\] in 5 min. It will cool down from \[{{100}^{o}}C\] to \[{{90}^{o}}C\] in (Assume cooling by radiation alone)
A.	More than 5 min
B.	less than 5 min
C.	5 min
D.	Can't be computed from information provided
Answer» C. 5 min

Discussion

1245.	If a shell fired from a cannon, explodes in mid air, then [Pb. PET 2004]
A.	Its total kinetic energy increases
B.	Its total momentum increases
C.	Its total momentum decreases
D.	None of these
Answer» B. Its total momentum increases

Discussion

1246.	A radioactive nucleus (initial mass number A and atomic number Z emits 3 \[\alpha -\]particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will be
A.	\[\frac{A-Z-8}{Z-4}\]
B.	\[\frac{A-Z-4}{Z-8}\]
C.	\[\frac{A-Z-12}{Z-4}\]
D.	\[\frac{A-Z-4}{Z-2}\]
Answer» C. \[\frac{A-Z-12}{Z-4}\]

Discussion

1247.	In Millikan?s oil drop experiment, an oil drop of mass \[16\times {{10}^{-6}}kg\] is balanced by an electric field of \[{{10}^{6}}V/m.\] The charge in coulomb on the drop, assuming \[g=10\,m/{{s}^{2}}\] is [UP SEAT 2005]
A.	\[6.2\times {{10}^{-11}}\]
B.	\[16\times {{10}^{-9}}\]
C.	\[16\times {{10}^{-11}}\]
D.	\[16\times {{10}^{-13}}\]
Answer» D. \[16\times {{10}^{-13}}\]

Discussion

1248.	The angular velocity of a wheel is 70 rad/sec. If the radius of the wheel is 0.5 m, then linear velocity of the wheel is [MH CET 2000]
A.	70 m/s
B.	35 m/s
C.	30 m/s
D.	20 m/s
Answer» C. 30 m/s

Discussion

1249.	Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed number of A and B nuclei will be:
A.	\[1:4\]
B.	\[5:4\]
C.	\[1:16\]
D.	\[4:1\]
Answer» C. \[1:16\]

Discussion

1250.	On the Celsius scale the absolute zero of temperature is at
A.	\[0{}^\circ C\]
B.	\[\,32{}^\circ C\]
C.	\[100{}^\circ C\]
D.	\[\text{ }273.15{}^\circ C\]
Answer» E.

Discussion

Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

If the K.E. of a body is increased by 300%, its momentum will increase by [JIPMER 1978; AFMC 1993; RPET 1999; CBSE PMT 2002]

A simple pendulum of length l has a brass bob attached at its lower end. Its period is T. If a steel bob of same size, having density x times that of brass, replaces the brass bob and its length is changed so that period becomes 2T, then new length is [MP PMT 2002]

In a seconds pendulum, mass of bob is 30 gm. If it is replaced by 90 gm mass. Then its time period will [Orissa PMT 2001]

A plate oscillated with time period ?T?. Suddenly, another plate put on the first plate, then time period [AIEEE 2002]

What will be the angular momentum of a electron, if energy of this electron in H-atom is 1.5eV (in J-sec)

A body of mass m kg is lifted by a man to a height of one metre in 30 sec. Another man lifts the same mass to the same height in 60 sec. The work done by them are in the ratio [MP PMT 1993]

The velocity of waves in a string fixed at both ends is 2 m/s. The string forms standing waves with nodes 5.0 cm apart. The frequency of vibration of the string in Hz is [SCRA 1998]

Which of the following is the example of transverse wave [CPMT 1999]

Standing waves are produced in a 10 m long stretched string. If the string vibrates in 5 segments and the wave velocity is 20 m/s, the frequency is [CBSE PMT 1997; AIIMS 1998; JIPMER 2000]

The electrochemical equivalent of magnesium is \[0.126\,mg/C\]. A current of 5 A is passed in a suitable solution for 1 hour. The mass of magnesium deposited will be [MP PMT 1995]

Assertion : The graph of total energy of a particle in SHM w.r.t., position is a straight line with zero slope. Reason : Total energy of particle in SHM remains constant throughout its motion.

Infinite springs with force constant k, 2k, 4k and 8k.... respectively are connected in series. The effective force constant of the spring will be [J & K CET 2004]

Two springs of constant \[{{k}_{1}}\]and \[{{k}_{2}}\]are joined in series. The effective spring constant of the combination is given by [CBSE PMT 2004]

A particle at the end of a spring executes simple harmonic motion with a period \[{{t}_{1}}\], while the corresponding period for another spring is \[{{t}_{2}}\]. If the period of oscillation with the two springs in series is T, then [AIEEE 2004]

The shortest wavelength in the Lyman series of hydrogen spectrum is 912 Å corresponding to a photon energy of 13.6 eV. The shortest wavelength in the Balmer series is about [MP PMT 2004]

The moment of inertia of a thin uniform rod of mass M and length L about an axis passing through its midpoint and perpendicular to its length is\[{{I}_{0}}\]. Its moment of inertia about an axis passing through one of its ends and perpendicular to its length is

A worker piles up sand onto a circular area of radius R. No sand is to spill onto the surrounding area. The coefficient of friction of sand on sand is \[\mu \]. The greatest volume of the sand that can be stored in the manner is

A wire of cross section 4 mm2 is stretched by 0.1 mm by a certain weight. How far (length) will be wire of same material and length but of area 8 mm2 stretch under the action of same force [Kerala PMT 2004]

Particle nature and wave nature of electromagnetic waves and electrons can be shown by

Which of the following is constructed on the principle of electromagnetic induction [MP PMT 2002]

In figure find the total magnification after two successive reflections first on \[{{M}_{1}}\] and then on \[{{M}_{2}}.\]

A series ac circuit consist of an inductor and a capacitor. The inductance and capacitance is respectively 1 henry and \[25\mu F.\] If the current is maximum in circuit then angular frequency will be [RPMT 1999]

Nuclear fission was discovered by

In the following reaction the value of X is \[_{7}{{N}^{14}}{{+}_{2}}H{{e}^{4}}\,\to \,X{{+}_{1}}{{H}^{1}}\]

?Stem Correction? in platinum resistance thermometers are eliminated by the use of [AIIMS 1998]

Unit of stress is [MP PMT 1984]

Assertion : It is essential that all the lines available in the emission spectrum will also be available in the absorption spectrum. Reason : The spectrum of hydrogen atom is only absorption spectrum.

The angle of polarisation for any medium is \[60{}^\circ \]The critical angle for this is

A body is executing S.H.M. When its displacement from the mean position are 4 cm and 5 cm, it has velocities \[10cm\,{{s}^{-1}}\] and \[8\,cm\,{{s}^{-1}}\] respectively. Its periodic time is

If a simple harmonic oscillator has got a displacement of 0.02 m and acceleration equal to \[2.0m{{s}^{-2}}\] at any time, the angular frequency of the oscillator is equal to [CBSE PMT 1992; RPMT 1996]

To make the frequency double of an oscillator, we have to [CPMT 1999]

What is constant in S.H.M. [UPSEAT 1999]

In Bohr?s model, if the atomic radius of the first orbit is \[{{r}_{0}}\], then the radius of the fourth orbit is [CBSE PMT 2000]

Mercury thermometers can be used to measure temperatures upto [CBSE PMT 1992, 96; BHU 1998; UPSEAT 1998]

A transformer is employed to reduce 220 V to 11 V. The primary draws a current of 5 A and the secondary 90 A. The efficiency of the transformer is [MP PMT 1992, 2001, 04]

Assertion : The percentage change in time period is 1.5%, if the length of simple pendulum increases by 3%. Reason : Time period is directly proportional to length of pendulum.

If a rod is in variable state (not in steady state), then

A body cools down from \[{{70}^{o}}C\] to \[{{60}^{o}}\] in 5 min. It will cool down from \[{{100}^{o}}C\] to \[{{90}^{o}}C\] in (Assume cooling by radiation alone)

If a shell fired from a cannon, explodes in mid air, then [Pb. PET 2004]

A radioactive nucleus (initial mass number A and atomic number Z emits 3 \[\alpha -\]particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will be

In Millikan?s oil drop experiment, an oil drop of mass \[16\times {{10}^{-6}}kg\] is balanced by an electric field of \[{{10}^{6}}V/m.\] The charge in coulomb on the drop, assuming \[g=10\,m/{{s}^{2}}\] is [UP SEAT 2005]

The angular velocity of a wheel is 70 rad/sec. If the radius of the wheel is 0.5 m, then linear velocity of the wheel is [MH CET 2000]

Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed number of A and B nuclei will be:

On the Celsius scale the absolute zero of temperature is at