Evaluation Procedures for Class X

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Questions and Answers

A thin plastic rod is bent into a circular ring of radius R. It is uniformly charged with charge density λ. The magnitude of the electric field at its center is :

λ / 2πε₀R

λ / 4πε₀R

zero (correct)

λ / 4πε₀R

Ten capacitors, each of capacitance 1 µF, are connected in parallel to a source of 100 V. The total energy stored in the system is equal to :

5.0 × 10⁻² J (correct)

10⁻² J

0.5 × 10⁻³ J

10⁻³ J

Consider the circuit shown in the figure. The potential difference between points A and B is :

8 V

12 V

6 V

9 V (correct)

A loop carrying a current I clockwise is placed in x – y plane, in a uniform magnetic field directed along z-axis. The tendency of the loop will be to :

shrink (B) Signup and view all the answers

A 10 cm long wire lies along y-axis. It carries a current of 1.0 A in the positive y-direction. A magnetic field B-> = (5 mT)j-> + (8 mT)k-> exists in the region. The force on the wire is :

-(80 mN)i-> (D) Signup and view all the answers

A galvanometer of resistance GΩ is converted into an ammeter of range 0 to I A. If the current through the galvanometer is 0.1% of I A, the resistance of the ammeter is :

G / (999) Ω (C) Signup and view all the answers

The reactance of a capacitor of capacitance C connected to an ac source of frequency ω is ‘X’. If the capacitance of the capacitor is doubled and the frequency of the source is tripled, the reactance will become :

X / 6 (A) Signup and view all the answers

In the four regions, I, II, III and IV, the electric fields are described as : Region I : Ex = Eo sin (kz – ωt) Region II : Ex = Eo Region III: Ex = Eo sin kz Region IV : Ex = Eo cos kz The displacement current will exist in the region :

I (D) Signup and view all the answers

The transition of electron that gives rise to the formation of the second spectral line of the Balmer series in the spectrum of hydrogen atom corresponds to :

n = 2 and n1 = 3 (A) Signup and view all the answers

Ge is doped with As. Due to doping,

the number of conduction electrons increases. (C) Signup and view all the answers

Two beams, A and B whose photon energies are 3.3 eV and 11.3 eV respectively, illuminate a metallic surface (work function 2.3 eV) successively. The ratio of maximum speed of electrons emitted due to beam A to that due to beam B is :

1 / 3 (B) Signup and view all the answers

Find the temperature at which the resistance of a wire made of silver will be twice its resistance at 20°C. Take 20°C as the reference temperature and temperature coefficient of resistance of silver at 20°C = 4.0 × 10⁻³ K⁻¹.

543 K Signup and view all the answers

Monochromatic light of frequency 5.0 × 10¹⁴ Hz passes from air into a medium of refractive index 1.5. Find the wavelength of the light (i) reflected, and (ii) refracted at the interface of the two media.

(i) 600 nm; (ii) 400 nm Signup and view all the answers

A plano-convex lens of focal length 16 cm is made of a material of refractive index 1.4. Calculate the radius of the curved surface of the lens.

6.4 cm Signup and view all the answers

An object is placed 30 cm in front of a concave mirror of radius of curvature 40 cm. Find the (i) position of the image formed and (ii) magnification of the image.

(i) -60 cm; (ii) -2 Signup and view all the answers

Consider a neutron (mass m) of kinetic energy E and a photon of the same energy. Let λn and λp be the de Broglie wavelength of neutron and the wavelength of photon respectively. Obtain an expression for λn / λp.

λn / λp = h / √(2mE) Signup and view all the answers

Plot a graph showing the variation of current with voltage for the material GaAs. On the graph, mark the region where : (a) resistance is negative, and (b) Ohm's law is obeyed.

The graph is typically a curve with a negative slope in the region where the resistance is negative, and a linear positive slope in the region where Ohm's law is obeyed. Signup and view all the answers

A cube of side 0.1 m is placed, as shown in the figure, in a region where electric field E-> = 500 x i-> exists. Here x is in meters and E in NC⁻¹. Calculate: (a) the flux passing through the cube, and (b) the charge within the cube.

(a) 0.5 N m² C⁻¹ ; (b) 4.4 × 10⁻¹² C Signup and view all the answers

Define ‘current density'. Is it a scalar or a vector ? An electric field E-> is maintained in a metallic conductor. If n be the number of electrons (mass m, charge – e) per unit volume in the conductor and its relaxation time, show that the current density j-> = aE-> , where α = (ne²/ m)τ

Current density is a vector quantity. It is the amount of charge flowing per second per unit area normal to the flow. Signup and view all the answers

What is a Wheatstone bridge? Obtain the necessary conditions under which the Wheatstone bridge is balanced.

A Wheatstone bridge is a circuit consisting of four resistors connected in a quadrilateral configuration to measure an unknown resistance. Signup and view all the answers

A proton with kinetic energy 1.3384 × 10⁻¹⁴ J moving horizontally from north to south, enters a uniform magnetic field B of 2.0 mT directed eastward. Calculate: (a) the speed of the proton (b) the magnitude of acceleration of the proton (c) the radius of the path traced by the proton [Take (q/m) for proton = 1.0 × 10⁸ C/kg]

(a) 4 × 10⁶ m/s; (b) 8 × 10¹¹ m/s²; (c) 20 m Signup and view all the answers

Flashcards

Rectification

The process of converting an alternating current (AC) voltage into a direct current (DC) voltage.

Rectifier

A device that converts AC voltage into DC voltage.