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Recent questions in Class12
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JEEMAIN and NEET
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Physics
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Class12
Class12
Electric Charges and Fields
Electrostatic Potential and Capacitance
Current Electricity
Moving Charges and Magentism
Magnetism and Matter
Electromagnetic Induction
Alternating Current
Electromagnetic Waves
Ray Optics and Optical Instruments
Wave Optics
Dual Nature of Matter and Radiation
Atoms
Nucleii
Semiconductor Materials and Electronic Devices
Communication Systems
Experimental Skills in Physics
Three charges Q, +q ans +q are placed at vertices of equilateral triangle. If total electric potential energy of system is zero, the value of Q will be :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatic-potential-energy-of-a-system-of-charges
easy
asked
Jan 8, 2014
by
meena.p
1
answer
Charges +q and -q are placed on vertices B and C of isosceles triangle. The potential at vertex A is :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatic-potential-energy-of-a-system-of-charges
easy
asked
Jan 8, 2014
by
meena.p
1
answer
The capacitors A and B are connected in series with a battery. When S is closed two capacitor gets fully charged , then :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
medium
asked
Jan 8, 2014
by
meena.p
1
answer
If $E_e$ be the electric field strength of a short dipole at a point on the equitorial line and $ E_a$ be that on axial line at same distance then :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-flux-and-dipole
easy
asked
Jan 6, 2014
by
meena.p
1
answer
16 dipoles of charge of magnitude e are placed inside a cube. The total electric flux coming out of the cube will be :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-flux-and-dipole
easy
asked
Jan 6, 2014
by
meena.p
1
answer
An alpha particle is accelerated by a potential difference of $10^7 V$. Its kinetic energy will be
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatic-potential
easy
asked
Jan 6, 2014
by
meena.p
1
answer
A $20 \mu F$ capacitor and $ 40 \; \mu F$ capacitor are connected in series across $400\; V$ supply line. The charged capacitors are then disconnected from the line and reconnected with their positive plates together and negative plates together. No external voltage is applied. What is potential difference across each capacitor .
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
A dielectric slab is introduced just to fill up the space between plates of parallel plate capacitor. The capacitor is charged and then disconnected . The slab is then slowly drown out . The plot of potential difference across the plates and length of dielectric slab drawn out looks like :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
effect-of-dielectric-on
capacitance
medium
asked
Jan 6, 2014
by
meena.p
1
answer
Choose incorrect statement : When two identical capacitors are charged individually to different potential, and connected to each other after disconnecting them from source .
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
An uncharged capacitor is connected to a battery. On charging the capacitor :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
parallel-plate-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
A capacitor is charged to $3200 V$ and then connected across a resistor of resistance R. If after 1 s potential difference across capacitor is 2400 V, What will be the potential difference across after 2 and 3 seconds .
jeemain
physics
class12
ch2
electrostatics
elecrostatic-potential-and-capacitior
parallel-plate-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
Two equal and opposite charges $ 8 \times 10^{-8} C$ are placed $ 2 \times 10^{-2} $ cm away from a dipole . If this dipole is placed in an external electric field $2 \times 10^8 N/C$. the value of maximum torque and work done in rotating through $180^{\circ}$ will be :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-flux-and-dipole
easy
asked
Jan 6, 2014
by
meena.p
1
answer
Region surrounding electric dipole
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
easy
asked
Jan 6, 2014
by
meena.p
1
answer
The capacitance of parallel plate capacitor does not depend upon
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
parallel-plate-capacitors
easy
asked
Jan 6, 2014
by
meena.p
3
answers
If a charge q is rotated around charge Q in a circle of radius y by $90^{\circ}$, the work done will be
jeemain
physics
class12
unit11
electrostatics
easy
sec-a
asked
Jan 6, 2014
by
meena.p
1
answer
Find the equivalent capacitance :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
Equivalent capacity of parallel plate capacitor shown below is :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
parallel-plate-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
In the circuit shown below ; if 2000 v potential is given to point A, the potential at point B is :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
The plates of parallel plate capacitor of capacity $ 100 \mu F$ are charged to potential $100 v $and then seperated from each other so that distance between them is doubled. How much energy is spent in doing so ?
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
parallel-plate-capacitors
easy
asked
Jan 6, 2014
by
meena.p
1
answer
A parallel plate capacitor of plate area A, plate seperation d is charged potential difference V. The battery is then removed and a slab of dielectric constant k is inserted between plates of capacitor. If $Q,\in $ and $w$ denotes charge , electric field (after slab is inserted ) and work done on the system in process of inserting the slab, the incorrect relation is :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
effect-of-dielectric-on-capacitor
medium
asked
Jan 3, 2014
by
meena.p
1
answer
A change A is divided into two parts: q and Q-q. if Coulomb repulsion between them when they are separated is maximum , $\large\frac{Q}{Q-q}$ should be :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
coulomb-law
medium
asked
Jan 3, 2014
by
meena.p
1
answer
To obtain $6 \mu F $ capacity from $3$ capacitors of $4 \mu F$ each, they will be arranged as :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitiors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
The electric potential as a function of distance x is given by $ V= (-5x ^2-10 x +9) \;volt$ . The electric field at point $(1,2)$ is
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatic-potential
easy
asked
Jan 3, 2014
by
meena.p
1
answer
A charge q is placed at middle point of the line joining two equal charges +Q. The value of q such that system is in equilibrium is :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
coulomb-law
easy
asked
Jan 3, 2014
by
meena.p
1
answer
A hollow metal sphere of radius 5 cm is charged such that the potential on its surface is 25 V. The electric field at centre of sphere is :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Two small spherical balls whose charges are $20 \mu c$ each are hanged with help of 1 m long thread from roof. In equilibrium both threads are seperated by $ 60^{\circ}$ Tension in each thread is :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
coulomb-law
easy
asked
Jan 3, 2014
by
meena.p
1
answer
A $0.4 \mu F$ capacitor is charged to $1200 v. $ After removing battery a $0.2 \mu F$ capacitor is connected in parallel to it. The voltage on capacitor will become :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Electric potential at any point is $V=-10 x +6y +\sqrt {60 }z$, then magnitude of electric field is :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatic-potential
easy
asked
Jan 3, 2014
by
meena.p
1
answer
If capacitor is changed from 0 to 20 v using constant current. Variation in energy U of capacitor with time t will be
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
parallel-plate-capacitors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
All the capacitors shown in circuit are identical . Each can withstand maximum $100 V$ between its terminals . The maximum voltage that can be applied safely b/w A and B is
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Two metal balls of same radii are charged to 5 and -25 units of electricity . They are brought in contact with each other and then again seperated to original distance. Ratio of magnitude of force b/w two balls after and before contact is
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
coulomb-law
easy
asked
Jan 3, 2014
by
meena.p
1
answer
In a medium of dielectric constant K, the electric field is $\overrightarrow {E}$, if $\in _0$ is permittivity of free space , the electric displacement vector is :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Potential of any point inside a charged hollow sphere :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrosatics-of-conductors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
A force F acts between two charges kept 1 cm apart in air. If permittivity of air and dielectric constant of water are $\in _0$ and $K$ respectively, find the force acting when both atoms are placed in water.
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
coulomb-law
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Total electric flux coming out of unit positive charge put in air is :
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
gausss-law
easy
asked
Jan 3, 2014
by
meena.p
1
answer
n identical condensers are joined in series and are charged to potential v. Now they are seperated and joined in parallel. Total energy and potential difference of combination will be :
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
combination-of-capacitors
easy
asked
Jan 3, 2014
by
meena.p
1
answer
Potential energy of a particle varies as a function of $x$ and is given as $ U(x)$ \[ \begin {bmatrix} E_{\circ} & 0 \leq x \leq 1 \\ 0 & x > 1 \end {bmatrix} \] The de-Broglie wavelengths of the particle in the region $ 0 \leq x \leq1$ and $x>1$ are $ \lambda_1$ and $ \lambda_2$ respectively. If the total energy of the particle is $2E_{\circ}$, the ratio $ \large\frac{\lambda_1}{\lambda_2}$is
jeemain
physics
dual-nature-matter-radiation
cbse
class12
wave-nature-of-matter
difficult
asked
Jan 1, 2014
by
thanvigandhi_1
1
answer
Assume that the de-Broglie wave associated with an electron can form a standing wave between the atoms arranged in a one dimensional array with nodes on each of the atomic site. It is found that one such standing wave is formed if the distance between the atoms of the array is $2\: A^{\circ}$ A similar standing wave is again formed if $d$ is increased to $2.5\: A^{\circ}$ . but not for any other intermediate value of $d$. The energy of the electron is
jeemain
physics
dual-nature-matter-radiation
cbse
class12
wave-nature-of-matter
difficult
asked
Jan 1, 2014
by
thanvigandhi_1
1
answer
Light of wavelength $4000\: A^{\circ}$ and intensity $100 W/m^2$ is incident on a plate of threshold frequency $ 5.5 \times 10^{14}Hz$. The no. of photons incident per $m^2$ per second is
jeemain
physics
dual-nature-matter-radiation
cbse
class12
difficult
q28
asked
Jan 1, 2014
by
thanvigandhi_1
1
answer
One milliwatt of light of wavelength of 4560 $A^{\circ}$ is incident on a cesium surface. Calculate the electron current liberated. Assume a quantum efficiency of 0.5%.
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Jan 1, 2014
by
thanvigandhi_1
1
answer
If the speed of photoelectrons is $10^4\: m/s$, what should be the frequency of the incident radiation on a potassium metal? (work function of potassium = $2.3 eV)$
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
A photosensitive metallic surface has work function, $hv_{\circ}$. If photons of energy $2hv_{\circ}$ fall on this surface, the electrons come out with a maximum velocity of $4 \times 10^6 \: m/s$. When the photon energy is increased to $5hv_{\circ}$, then maximum velocity of photoelectrons will be
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
Threshold wavelength for photoelectric emission from a metal surface is 5200 $A^{\circ}$ will be emitted when this surface is illuminated with monochromatic radiation from . Photoelectrons
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
Figure shows the variation of photocurrent with anode potential for a photo-sensitive surface for three different radiations
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
A photon of energy 4 eV is incident on a metal surface whose work function is 2 eV. The minimum reverse potential to be applied for stopping the emission of electrons is
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
In a series of photoelectric emission experiments, a number of different metals were illuminated with monochromatic light of a number of different photon energies and of different intensities. The variables in the experiment were thus:
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
In which of the following cases the heavier of the two particles has a smaller de-Broglie wavelength? The two particles
jeemain
physics
dual-nature-matter-radiation
cbse
class12
wave-nature-of-matter
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
Figure shows the results of an experiment involving photoelectric effect. The graphs A,B,C,D relate to light beams having different wavelengths.
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the cut- off voltage and the saturation current are respectively 0.6 V and 18 mA. If the same source is placed 0.6 m away from the photocell, then choose the correct option:
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
Which of the following statements is not in support of the quantum nature of light?
jeemain
physics
dual-nature-matter-radiation
cbse
class12
photoelectric-effect
difficult
asked
Dec 31, 2013
by
thanvigandhi_1
1
answer
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