// objective questions related to elecrostatic forces
(1)A ring of radius 6 c.m is given a charge 10 micro columb .how much work will be done in transporting a charge of 6micro columb from its centre to a point 8 c.m along its axis?
(A)63mJ
in the strings ,then it could be said that while making the above changes in tension
(B) 84mJ
(C) 105mJ
(D) 126mJ
(2) Which of the following combinations of seven identical capacitorseach of 2micro faraday gives a capacitance of 9.09micro faraday?
•5 in parallel with 2 in series.
•4 in parallel with 3 in series.
•3 in parallel with 4 in series.
•2 in parallel with 5 in series.
(3) Two resistances when connnected in parallel have equal resistance of 3ohm. When one of the resistance is burnt and broken,the net resistance is 12 ohm.what will be the resistance of the burnt resistor?
(A)4ohm
(B) 8ohm
(C) 12ohm
(D) 16ohm
(4) The lamp of flash night is 1.5 ohm. It uses 3cells of 1.5Vand internal resistance of 0.25 ohm.what is the net potential difference across the lamp?
•1.5V
•2.25V
•3V
•4.5V
waves and oscillations
(5)Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously .on changin the tension slightly in one of them ,the beat frequency remain unchanged.Denoting by X & Y the higher and lower initial tension Y was decreased
•Y was increased
•X was increased
•X was decreased
(6) A tuning-fork vibrating with sonometer having 20 cm.wire produces 5beats/second . The beat frequency does not change if the length of wire is changed to 21 cm . The frequency of the tuning fork is (in hertz) must be
•200
•210
•205
•215
(7) A closed organ pipe (closed at one end) is excited to supportthe third overtone.itis found that air in the pipe has
•Three nodes and three antinodes
•Three nodes and four antinodes
•Four nodse and three antinodes
•Four nodes and four antinodes
(8) If the pressure amplitude in a sound wave is tripled then by what factorthe intensity of sond wave is increased?
•3
•6
•9
•1.732
(9) The distance between tow points differing in phase by 60 degree on a wave having a wave velocityof 360m/sec. and frequency 500hz is
•0.72m
•0.12m
•0.18m
•0.36m
(10) A stone is droppped into a lake from a tower 500m high . The sound of splash will be heard by the man approximately after
•11.5 sec
•21 sec
•10 sec
•14 sec
(11) The velocity of sound change in air is independent of change in
•Pressure
• Density
•Temperature
•Humidity
(12) A sound sorce of frequency in 170hz is placed near a wall. A man walking from the source normally towards the wall from the source normally towards the wall from the source finds that there is a periodic rise & fall of sound intensity. If speed of sound in air is 340m/sec.,the distance in metres sepsrating the two adjacent position of minium intensity is
•0.5
•1
•1.5
•2
(13) A 5.5 m length of string has a mass of 0.035kg.If the tension in the string in 77N,the speed of a wave on the string is
(A) 110 m/sec.
(B) 165 m/sec.
(C) 77 m/sec.
(D) 102 m/sec.
(14) A closed organ pipe & an organ pipe have their first overtone identical in frequency.their lengts are in the ratio
•1:2
• 2:3
• 3:4
• 4:5
(15) An open pipes is suddenly closed with the result that he second overtone of the closed pipe is found to be higherl in frequecy. By 100 hz.than the first overtone of the original pipe. Th fundanental frequency of open well will be
•100 hz
•300 hz
•150 hz
•200 hz
(16) If the resonance tube , using the turning fork of frequency 325 hz ,tow resonance length are observedas 25.4 cm & 77.4 cm respectively.the velocity of sound in air is
•338 m/sec.
•328 m/sec.
•330m/sec.
•320m/sec.
(17) The velocity of the sound is generally greater in solids than in gases because
(A) The distance of the solid is high but the elasticity is low.
(B) The density of the solids is high but the elasticity of solids is very high.
(C) Both the density and the elasticity of the solids are low.
(D) The density of solids is low but the elasticity is high.
(18) The interference phenonmena can take plase in
•All waves
•Transverse waves only
•Longitudinal waves only
•Standing waves only
(19) A string under a tension of 129.6N produces 10 beats/sec.,when it is vibrated along with a tuning fork . When the tension in the string is increased to 160N ,its sound in unison with the same tuning fork .then frequency in tuning fork is
•100 hz
•90 hz
•110 hz
•220 hz
(20) A glass tube of 1.0m length is filled with water.the water can be drained out slowly at the bottom of the tube . If the vibrating tuning fork of frequency 500 hz is brought at the upper end of the tube and the velocity of the sound is330m/sec. then the total no. of resonances obtained will be
•4
•3
•2
•1
(21) In the case of a moving source of sound approaching an observer
•The wavelength of sound appears to be less.
•The wavelength of sound appears to be more.
•The frequency appears to be less.
• none of these.
MCQ of ‘Sources of emf’
(1)The dimension of the emf of a source of current are that of :
•Force
•Electric field
•Current
•Potential
(2) The electric cell is a device to obtain:
•Electrons
•Electric charge
• Electric energy from chemical energy
•Electric force
(3) within the electric cell , the chrge is transported by:
•Free electrons
•Only positive ions
•Only negative ions
•Positive ions and negative ions.
(4) First electrocemical cell was designed by :
•Galvani
•Faraday
•Leclanche
•Some one another then those mentionrd above .
(5) which of the following is not the disadvantage of polarization of voltaic cell?
•Increase in internal resistance.
•Wastage of chemical energy.
•Setting up of back emf.
•Decrease in current supply.