In electromagnetic waves the phase difference between electric and magnetic field vectors are

Choose the correct statement.

In an a.c. generator, a coil with N turns, all of the same area A and total resistance R, rotates with frequency ω in a magnetic field B the maximum value of emf generated in the coil is

In a coil of resistance 10π, the induced current developed by changing magnitude of change in flux through the coil is weber is

Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator

An electric dipole is kept in a non-uniform electric field. It experiences

Advantage of reflecting telescopes are

A long solenoid has 20 turns cm^-1. The current necessary to produce a magnetic field of 20 mT inside the solenoid is approximately

A potential difference of 100 V is applied to the ends of a copper wire one metre long. What is the average drift velocity of electrons?
(given. σ = 5.81 x 10⁷ Ω^-1or n_cu = 8.5 x 10²⁸ m^-3)

Two protons are attracting each other, then separation between them is

The resistance of a 10 m long wire is 10Ω. Its length is increased by 25%by stretching the wire uniformly. The resistance of wire will change to

What is the value of capacitance if a very thin metallic plate is introduced between two parallel plates of area A and separated at distance d?

Two charges 3 x 10^-8 C and - 2 x 10^-8 C located 15 cm apart. At what point on the line joining the two charges is the electric potential zero?

Total electric flux coming out of a unit positive charge put in air is

A magnifying glass of focal length 5 cm is used to view an object by a person whose smallest distance of distinct vision is 25cm. If he holds the glass close to eye, then the magnification is

The de-Broglie wavelength of the tennis ball of mass 60g moving with a velocity of 10m/s is approximately: (Plank's constant h = \(h=6.63\times { 10 }^{ -34 }Js\)

The relation \(\frac { { E }_{ s } }{ { E }_{ p } } =\frac { { n }_{ s } }{ { n }_{ p } } \) is applied only to

In a sample of radioactive substance, what percentage decays in one mean life time?

Polarizing angle for a medium is \(60°\) . Its refractive index is

When an electric field is applied across a semiconductor

Assertion (A): The Heisenberg uncertainty principle states that it is impossible to simultaneously determine the exact position and momentum of an electron.
Reason (R): The act of measurement of position and momentum of an electron disturbs the electron’s state, making it impossible to know both properties with certainty.
Codes:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Assertion : The work function of a metal is the minimum energy required to release an electron from its surface.
Reason : For the photoelectric effect to occur, the energy of incident photons must be greater than or equal to the work function of the metal.
Codes:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Assertion : It is not possible to use ³⁵Cl as the fuel for fusion energy.
Reason : The binding energy of ³⁵Cl is to small.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Assertion (A) : Microscope magnifies the image.
Reason (R) : Angular magnification for image is more than object in microscope
Codes:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other.
Reason : The fringe width is inversely proportional to the distance between the two sources.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Assertion : A step up transformer can also as a step down transformer.
Reason : This is because
Codes:
(a) If both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
(c) If Assertion is true but the Reason is false.
(d) If Assertion & Reason both are false.

Assertion : A laminated core is used in transformers to increase eddy currents.
Reason: The efficiency of a transformer increases with increase in eddy currents.
Codes:
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

Assertion : The surface densities of two spherical conductors of different radii are equal. Then the
electric field intensities near their surface are also equal.
Reason : Surface density is equal to charge per unit area.
Codes:
(a) Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) Assertion is correct, Reason is incorrect
(d) Both Assertion and Reason are correct.

Assertion : If the current in a solenoid is reversed in direction while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.
Reason : Magnetic field energy density is proportional to square of current.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Assertion: Current is a scalar quantity.
Reason: Electric current arises due to continuous flow of charged particles or ions.
Codes:
 (A) If both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
 (B) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
 (C) If Assertion is true but the Reason is false
 (D) If Assertion & Reason both are false.

Assertion : When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system decreases.
Reason : The force between the plates decreases.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Assertion (A) : Propagation of light through an optical fibre is due to total internal reflection taking place at the core-clade interface,
Reason (R) : Refractive index of the material of the core of the optical fibre is greater than that of air.
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

Assertion (A) : When the capacitor is connected to an AC source, it limits or regulates the current, but does not completely prevent the flow of charge.
Reason (R) : The capacitor is alternately charged and discharged as the current reverses each half-cycle.
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

Assertion (A) The electrical conductivity of a semiconductor increases on doping.
Reason (R) Doping always increases the number of electrons in the semiconductor.
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

Assertion (A) Electrons are ejected from the surface of zinc when it is irradiated by yellow light.
Reason (R) Energy associated with a photon of yellow light is more than the work function of Zinc.
(a) If both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) If both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
(c) If Assertion (A) is true and Reason (R) is false.
(d) If both Assertion (A) and Reason (R) are false.

Assertion (A) : When number of turns in a coil doubled, coefficient of self inductance of the coil becomes four times.
Reason (R) : Coefficient of self inductance is proportional to the square of number of turns.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

Assertion (A) : At neutral point, a compass needle point out in any arbitrary direction.
Reason (R) : Magnetic field of earth is balanced by field due to magnets at the neutral points
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

Assertion: Material used in the construction of a standard resistance is constant an or manganin.
Reason: Temperature coefficient of constantan is very small.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

Assertion (A) : A capacitor is connected to a battery. If we move its plate further apart, work will be done against the electrostatic attraction between the plates and the energy of the capacitor gets decreased.
Reason (R) : The energy stored in capacitor is dissipated in the form of heat energy.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

Assertion (A) : Charging is due to transfer of electrons.
Reason (R) : Mass of a body decreases slightly when it is negatively charged.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

The nuclear charge(Ze) is non-uniformly distributed within a nucleus of radius R. The charge density p(r) [charge per unit volumne is dependent only on the radial distance r from the centre of the nucleus as shown in figure.The electric field is only along the radial direction.

(i) The electric field at r= R is
(a) independent of a
(b) directly proportional to a 
(c) directly proportional to \(a^2\)
(d) inversely proportional to a
(ii) Net charge on given system is
\(\text { (a) } Q=\int \rho_r\left(4 \pi r^2\right) d r\)
\(\text { (b) } Q=\int \rho_r\left(\pi r^2\right) d r\)
\(\text { (c) } Q=\int \rho_r \frac{r^2}{2} d r\)
\(\text { (d) } Q=\int \rho_r\left(4 \pi r^2\right)\)
(iii) For a =0, the value d (maximum value ofp as shown in the figure) is
\(\text { (a) } \frac{3 Z e^2}{4 \pi R^3}\)
\(\text { (b) } \frac{3 Z e}{\pi R^3}\)
\(\text { (c) } \frac{4 Z e}{3 \pi R^3}\)
\(\text { (d) } \frac{Z}{3 \pi R^3}\)
(iv) The correct graph representing the variation of E with r is

(v) The electricfield within the nucleus is generally observed to be linearly dependent on r. This implies
(a) a =0
\(\text { (b) } a=\frac{R}{2}\)
(c) a= R
\(\text { (d) } a=\frac{2 R}{3}\)

To study photoelectric effect, an emitting electrode C of a photosensitive material is kept at negative potential and collecting electrode A is kept at positive potential in an evacuated tube. When light of sufficiently high frequency falls on emitting electrode, photoelectrons are emitted which travel directly to collecting electrode and hence an electric cusrent called photoelectric current starts flowing in the circuit, which is directly proportional to the number of photoelectrons emitted by emitting electrode C.

While demonstrating the existence of electromagnetic waves, Hertz found that high voltage sparks passed across the metal electrodes of the detector loop more easily when the cathode was illuminated by ultraviolet light from an arc lamp. The ultraviolet light falling on the metal surface caused the emission of negatively charged particles,which are now known to be electrons, into the surrounding space and hence enhanced the high voltage sparks.
(i) Cathode rays were discovered by

(a) Maxwell Clerk James	(b) Heinrich Hertz
(c) William Crookes	(d) J. J. Thomson

(ii) Cathode rays consists of

(a) photons

(b) electrons

(c) pistons

(d) a-particles.

(iii) Who discovered the charge on an electron for the frist time?

(a) Millikan

(b) Thomson

(c) Kelvin

(d) Coulomb

(iv) The dual nature of light is exhibited by

(a) diffraction and photoelectric effect	(b) photoelectric effect
(c) refraction and interference	(d) diffraction and reflection

(v) In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of

(a) collisions between the charged particles emitted from the cathode and the atoms of the gas

(b) collision between different electrons of the atoms of the gas

(c) excitation of electrons in the atoms

(d) collision between the atoms of the gas.

The flow of charge in a particular direction constitutes the electric current. Current is measured in Ampere. Quantitatively, electric current in a conductor across an area held perpendicular to the direction of flow of charge is defined as the amount of charge is flowing across that area per unit time.
Current density at a point in a conductor is the ratio of the current at that point in the conductor to the area of cross section of the conductor of that point.
The given figure shows a steady current flows in a metallic conductor of non uniform cross section. Current density depends inversely on area, so, here \(J_{1}>J_{2}, \text { as } A_{1}.

(i) What is the current flowing through a conductor, if one million electrons are crossing in one millisecond through a cross-section of it ?

(a) 2.5 x 10-10 A	(b) 1.6 x 10-10 A
(c) 7.5 X 10-9 A	(d) 8.2 x 10-11 A

(ii) SI unit of electric current is

(a) Cs

(b) Ns-2

(c) Cs-1

C-1s-1

(iii) A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor?

(a) Electric field

(b) Drift velocity

(c) Current

(d) Current density

(iv) A constant current I is flowing along the length of a conductor of variable cross-section as shown in the figure. The quantity which does not depend upon the area of cross-section is

(a) electron density	(b) current density
(c) drift velocity	(d) electric field

(v) When a current of 40 A flows through a conductor of area 10 m², then the current density is

(a) 4 A/m2

(b) 1 A/m2

(c) 2 A/m2

(d) 8 A/m2

For the various charge systems, we represent equipotential surfaces by curves and line of force by full line curves. Between any two adjacent equipotential surfaces, we assume a constant potential difference the equipotential surfaces of a single point charge are concentric spherical shells with their centres at the point charge. As the lines of force point radially outwards, so they are perpendicular to the equipotential surfaces at all points.

(i) Identify the wrong statement.

(a) Equipotential surface due to a single point charge is spherical.

(b) Equipotential surface can be constructed for dipoles too.

(c) The electric field is normal to the equipotential surface through the point.

(d) The work done to move a test charge on the equipotential surface is positive

(ii) Nature of equipotential surface for a point charge is

(a) Ellipsoid with charge at foci	(b) Sphere with charge at the centre of the sphere
(c) Sphere with charge on the surface of the sphere	(d) Plane with charge on the surface

(iii) A spherical equipotential surface is not possible

(a) inside a uniformly charged sphere	(b) for a dipole
(c) inside a spherical condenser	(d) for a point charge

(iv) The work done in carrying a charge q once round a circle of radius a with a charge Q at its centre is

\(\text { (a) } \frac{q Q}{4 \pi \varepsilon_{0} a}\)

\(\text { (b) } \frac{q Q}{4 \pi \varepsilon_{0} a^{2}}\)

\(\text { (c) } \frac{q}{4 \pi \varepsilon_{0} a}\)

(d) zero

(v) The work done to move a unit charge along an equipotential surface from P to Q

(a) must be defined as \(-\int_{P}^{Q} \vec{E} \cdot d \vec{l}\)	(b) is zero
(c) can have a non-zero value	(d) both (a) and (b) are correct