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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
An electric bulb is rated $220V$- $100W$. The power consumed by it when it operates on $110V$ is
jeemain
physics
current-electricity
cbse
class12
ch5
electrical-energy-and-power
easy
asked
Feb 16, 2014
by
thanvigandhi_1
1
answer
The resistance of a bulb filament is $ 100\Omega$ at a temperature of $100^{\circ}C$. If its temperature coefficient of resistance be $0.005 \: per^{\circ}C$ its resistance will become $200\Omega$ at a temperature of
jeemain
physics
current-electricity
cbse
class12
ch5
temperature-dependence-of-resistance
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
In a Wheatstone's bridge their resistances P, Q and R connected in the three arms and the fourth arm is formed by the two resistances $S_1\: and \: S_2$ connected in parallel. The condition for bridge to be balanced will be
jeemain
physics
current-electricity
cbse
class12
ch5
meter-bridge-potentiometer-instrumentation
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
Which of the following units denote the dimensions of $\large\frac{ML^2}{Q^2}$ , where $Q$ denotes electric charge
jeemain
physics
electromagnetic-induction
cbse
class12
ch6
inductance
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
The Kirchhoff’s first law $ (\sum i = 0)$ and second law $(\sum iR = \sum E)$ where symbols have their usual meanings, are respectively based on conservation of
jeemain
physics
current-electricity
cbse
class12
ch5
kirchhoffs-law
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A material B has twice the specific resistance of A. A circular wire made of B has twice the diameter of a wire made of A. Then for the two wires to have the same resistance, the ratio $ \large\frac{l_A}{l_b}$ of their respective lengths must be
jeemain
physics
current-electricity
cbse
class12
ch5
resistivity
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100W and 200V lamp when not in use?
jeemain
physics
current-electricity
cbse
class12
ch5
electrical-energy-and-power
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of $ 2 \Omega$ the balancing length becomes 120 cm. The internal resistance of the cell is
jeemain
physics
current-electricity
cbse
class12
ch5
meter-bridge-potentiometer-instrumentation
difficult
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
An energy source will supply a constant current into the loads of its internal resistance is
jeemain
physics
current-electricity
cbse
class12
ch5
cells-emf-internal-resistance
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A coil of inductance 300 mH and resistance $2\Omega$ is connected to a source of voltage 2V. The current reaches half of its steady state value in
jeemain
physics
alternating-current
cbse
class12
ch7
ac-voltage-applied-to-inductor
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A parallel plate capacitor is made by stacking $n$ equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C then the resultant capacitance is
jeemain
physics
electrostatics
electrostatic-potential-and-capacitance
cbse
class12
ch4
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be
jeemain
physics
current-electricity
cbse
class12
ch5
electrical-energy-and-power
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
Two sources of equal emf are connected to an external resistance R. The internal resistance of the two sources are $R_1\: and \: R_2 (R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$ is zero then,
jeemain
physics
current-electricity
cbse
class12
ch5
cells-emf-internal-resistance
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
In the circuit the galvanometer $G$ shows zero deflection. If the batteries A and B have negligible internal resistance, the value of the resistor $R$ will be
jeemain
physics
current-electricity
cbse
class12
ch5
ohms-law
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
Two voltameters one of copper and other of silver, are joined in parallel. When a total charge $q$ flows through a voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1\: and \: z_2$ respectively the charge which flows through the silver voltameter is
jeemain
physics
current-electricity
cbse
class12
ch5
chemiocal-effect-of-current
difficult
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be
jeemain
physics
current-electricity
cbse
class12
ch5
meter-bridge-potentiometer-and-instrumentation
difficult
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
Let $ \varepsilon_0$ denote the dimensional formula of the permittivity of vacuum. If M = mass, L = length and T = time and A = electric current then,
jeemain
physics
electrostatics
electric-charges-and-fields
cbse
class12
ch3
q113
difficult
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
In an LCR circuit as shown below both switches are open initially . Now switch $S_1$ is closed $S_2$ kept open. ( q is charge on the capacitor and $\tau = RC$ is capacitive time constant ) which of the following statement is correct ?
jeemain
physics
electromagnetic-induction
cbse
class12
ch6
inductance
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
What is the dimensional formula for inductance?
jeemain
physics
electromagnetic-induction
cbse
class12
ch3
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
What is the dimensional formula for capacitance?
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
easy
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
What is the dimensional formula for resistivity?
jeemain
physics
current-electricity
cbse
class12
ch5
resistivity
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
A 5V battery with internal resistance $2\Omega$ and a 2V battery with internal resistance $1\Omega$ are connected to a $ 10 \Omega $ resistor as shown in the figure. The current in the $ 10\Omega $ resistor is
jeemain
physics
current-electricity
cbse
class12
ch5
ohms-law
medium
asked
Feb 15, 2014
by
thanvigandhi_1
1
answer
An equi - convex lens of crown and equi convex lens of flint glass make an achromatic system. The radium of curvature of convex lens is $0.54\;m$. If the focal length of combination for mean colour is 1.5 m and $RI$ for crown glass are $\mu _R= 1.53$ and $\mu_v =1.55$ Then the dispersive power of flint glass is
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
refraction-by-prism
dispersion
difficult
asked
Feb 14, 2014
by
meena.p
1
answer
Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. We apply superposition principle to find voltage $ \Delta V$ developed between B and C. The calculation is done in the following steps. \[\] (i) Take current I entering from A and assume it to spread over a hemispherical surface in the block. \[\] Calculate field E(r) at distance r from A by using ohm's law $E= \rho j$, where j is the current per unit area at r. \[\] (iii) From the r dependence of E(r) obtain the potential V(r) at r. \[\] (iv) Repeat (i), (ii) and (iii) for current I leaving D and superpose results for A and D \[\] For current entering at A, the electric field at a distance r from A is
jeemain
physics
current-electricity
cbse
class12
ch5
ohms-law
gausss-law
medium
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. Apply the superposition principle and find the voltage $ \Delta V$ developed between B and C?
jeemain
physics
current-electricity
cbse
class12
ch5
ohms-law
difficult
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
In a YDSE $\lambda =60 \;nm\; D= 2m\;\lambda=6 mm$. Find the positions of a point lying b/w third maxima and third minima where the intensity in three - fourth of maximum intensity on the screen .
jeemain
physics
class12
unit16
wave-optics
youngs-double-slit-experiment
difficult
asked
Feb 14, 2014
by
meena.p
1
answer
When the screen is moved away from plane of slits in YDSE then the effect on interference fringes is
jeemain
physics
class12
unit16
wave-optics
youngs-double-slit-experiment
medium
asked
Feb 14, 2014
by
meena.p
1
answer
In an interference arrangement similar to YDSE , Slits $S_1\;and \;S_2$ are illuminated with coherent microwave sources and are synchronized to have zero phase difference The slits are separates by distance $d= 150 \;m$. The intensity $I_0$ is measured as a function of $\theta$ where $\theta$ is defined as shown. If $I _0$ is max intensity, calculate $I_0$ for $\theta=90^{\circ}$
jeemain
physics
class12
unit16
wave-optics
youngs-double-slit-experiment
difficult
asked
Feb 14, 2014
by
meena.p
1
answer
A parallel plate capacitor with air between the plates has a capacitance of $9\: pF$. The separation between the plates is $d$ . The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $k_1=3$ and thickness $ \large\frac{d}{3}$ while the other has dielectric constant $k_2=6$ and thickness $ \large\frac{2d}{3}$. Capacitance of the capacitor is now
jeemain
physics
cbse
class12
ch4
electrostatics
electrostatic-potential-and-capacitance
effect
-of-dielectric-on-capacitance
medium
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
Shown in the figure below is a meter-bridge setup with null deflection in the galvanometer.The value of the unknown resistor $R$ is
jeemain
physics
current-electricity
cbse
class12
ch5
meter-bridge-and-potentiometer-instrumentation
easy
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
A thin plano- convex lens of focal length f is split into two halves one of halves is shifted along the optical axis. The separation b/w object and image plane is 1.8 m. The magnification of image formed by one of half lenses is 2. Find the focal length of lens and separation b/w the two halves.
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
refraction-at-spherical-surfaces-and-lenses
medium
asked
Feb 14, 2014
by
meena.p
1
answer
Calculate the effective resistance between points A and B
jeemain
physics
current-electricity
cbse
class12
ch5
equivalent-resistance
medium
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
What is the average drift speed of conduction electrons in a copper wire of cross-sectional area $1.0 \times 10^{–7}m^2$ carrying a current of $1.5 A$. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $ 9.0 \times 10^3 kg/m^3 $ , and its atomic mass is $ 63.5 u.$
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
difficult
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
The cross section of glass prism has the form of an isosceles triangle . One of equal face is silvered. A ray of light incident normally on other equal face and after being reflected twice, emerges through base of prism along normal. That the angle of prism is :-
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
reflection-by-mirrors
medium
asked
Feb 14, 2014
by
meena.p
1
answer
At what temperature would the temperature of a copper conductor be double its value at $0^{\circ}C\: \alpha_{Cu} = 4 \times 10^{-3}$
jeemain
physics
current-electricity
cbse
class12
ch5
resistivity
medium
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
Which of the following is an example of ohmic conductor:
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
easy
asked
Feb 14, 2014
by
thanvigandhi_1
1
answer
Two identical charged spheres are suspended by strings of equal length . The strings make an angle of $\;60^{0}\;$ with each other . When suspended in a liquid of density $\;0.5 g/cc,\;$ the angle remains the same . The dielectric constant of the liquid is [density of material of sphere is $\;1.5 g/cc\;$]
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
difficult
asked
Feb 14, 2014
by
yamini.v
2
answers
A lens has a power of +5 diopter in air what will be its power if completely immersed in water ? $ \mu_g =\large\frac{3}{2};$$ \mu_w=\large\frac{4}{3}$
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
refraction-at-spherical-surfaces-and-lenses
medium
asked
Feb 14, 2014
by
meena.p
1
answer
A point source of light is placed at the bottom of a tank containing a liquid $(R.I= \mu)$ upto a depth $h$. A bright circular spot is seen on the surface of the liquid. Then the radius of this bright spot.:
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
total-internal-reflection
difficult
asked
Feb 14, 2014
by
meena.p
1
answer
In the figure shown for an angle of incidence i at the top surface , What is the minimum refractive index needed for total internal reflection at vertical face ?
jeemain
physics
class12
unit16
ray-optics-and-optical-instruments
total-internal-reflection
difficult
asked
Feb 14, 2014
by
meena.p
1
answer
A particle of mass m and charge +q is projected from the origin with a speed v at an angle $\;30^{0}\;$ with the horizontal into an electric field of intensity E directed downward . Equation of trajectory of particle is . Neglect gravity
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
difficult
asked
Feb 14, 2014
by
yamini.v
1
answer
A particle of charge -q and mass m moves in a circle of radius r arround an infinitely long line charge of linear density $\;+\lambda\;$ . Then time period will be
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
continuous-charge-distribution
difficult
asked
Feb 14, 2014
by
yamini.v
1
answer
Three concentric spherical metallic shells A , B and C of radii a , b and c $\;(a < b < c)\;$ have charge densities $\;\sigma , - \sigma \; and \; \sigma\;$ respectively . If the shells A and C are at the same potential then the relation between a , b and c is
jeemain
physics
class12
ch2
electrostatics
electrostatic-potential-and-capacitance
electrostatics-of-conductors
difficult
asked
Feb 14, 2014
by
yamini.v
1
answer
A 10.0 Kg block carrying a charge 100 $\;\mu C\;$ is connected to a spring for which $\;K=100 N/m\;$ . The block lies on a frictionless horizontal track , and the system is immersed in a uniform electric field $\;E=5\times10^{5}\;V/m\;$ , directed as shown in figure . If the block is released from rest when the spring is amount does the spring expand
jeemain
physics
class12
ch1
electrostatics
electric-charges-and-fields
electric-field
difficult
asked
Feb 14, 2014
by
yamini.v
1
answer
A point charge q is placed on the top of a cone of serni-vertex angle $\;\theta\; $ Find the electric flux through the base of the cone
jeemain
physics
class12
electric-charges-and-fields
electrostatics
gausss-law
difficult
asked
Feb 14, 2014
by
yamini.v
1
answer
The current in the primary circuit of a potentiometer is $0.2 A$. The specific resistance and cross-section of the potentiometer wire are $4 \times 10^{-7} ohm $ meter and $8 \times 10^{-7} \: m^2$ respectively. The potential gradient will be equal to:
jeemain
physics
current-electricity
cbse
class12
ch5
meter-bridge-potentiometer-and-instrumentation
easy
asked
Feb 13, 2014
by
thanvigandhi_1
1
answer
If $400ohms $ of resistance is made by adding four $ 100 \: ohm $ resistances of tolerance 5%, then the tolerance of the combination is:
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
easy
asked
Feb 13, 2014
by
thanvigandhi_1
1
answer
Time constant of a $RC$ circuit is $2/ln(2) s$. Capacitor is discharged at time $ t = 0$. The ratio of charge on the capacitor at time $t = 2s$ and $t = 6s$ is
jeemain
physics
electromagnetic-induction
cbse
class12
ch3
q98
easy
asked
Feb 13, 2014
by
thanvigandhi_1
1
answer
The potential difference across the terminals of the battery (with $2\;ohms$ internal resistance) is
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
easy
asked
Feb 13, 2014
by
thanvigandhi_1
1
answer
The current passing through the $ 3\Omega$ resistor is
jeemain
physics
current-electricity
cbse
class12
ch5
electric-current-concepts
easy
asked
Feb 13, 2014
by
thanvigandhi_1
1
answer
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