Wavefront is the locus of all points, where the particles of the medium vibrate with the same

• phase

• amplitude

• frequency

• period

Two identical charged spheres of material density ρ, suspended from the same point by inextensible strings of equal length make an angle θ between the strings. When suspended in a liquid of density σ the angle θ remains the same. The dielectric constant K of the liquid is

• $\frac{\mathrm{\rho }}{\mathrm{\rho } - \mathrm{\sigma }}$

• $\frac{\mathrm{\rho } - \mathrm{\sigma }}{\mathrm{\rho }}$

• $\frac{\mathrm{\rho }}{\mathrm{\rho } + \mathrm{\sigma }}$

• $\frac{\mathrm{\rho } + \mathrm{\sigma }}{\mathrm{\rho }}$

23.

The electric field at a point due to an electric dipole, on an axis inclined at an angle θ (< 90°) to the dipole axis, is perpendicular to the dipole axis, if the angle θ is

• tan^-1 (2)

• ${\tan }^{-1}\left(\frac{1}{2}\right)$

• ${\tan }^{-1} \left(\sqrt{2}\right)$

• ${\tan }^{-1}\left(\frac{1}{\sqrt{2}}\right)$

In the circuit shown, the currents i₁ and i₂ are

• i₁ = 1.5 A, i₂ = 0.5 A

• i₁ = 0.5 A, i₂ = 1.5 A

• i₁ = 1 A, i₂ = 3 A

• i₁ = 3 A, i₂ = 1 A

In the given network, the valve of C, so that an equivalent capacitance between points A and B is 3 µF, is

• $\frac{1}{5} \mathrm{\mu F}$

• $\frac{31}{5} \mathrm{\mu F}$

• 48 μF

• 36 μF

A conductor wire having 10²⁹ free electrons / m³ carries a current of 20A. If the cross-section of the wire is 1 mm², then the drift velocity of electrons will be (e = 1.6 × 10^-19 C)

• 1.25 × 10^-4 ms^-1

• 1.25 × 10^-3 ms^-1

• 1.25 × 10^-5 ms^-1

• 6.25 × 10^-3 ms^-1

A resistor has a colour code of green, blue, brown and silver. What is its resistance ?

• 56 Ω ± 5 %

• 560 Ω ± 10 %

• 560 Ω ± 5 %

• 5600 Ω ± 10 %

The voltage V and current I graph for a conductor at two different temperatures T₁ and T₂ and shown in the figure. The relation between T₁ and T₂ is

• T₁ > T₂

• T₁ < T₂

• T₁ = T₂

• ${\mathrm{T}}_1 = \frac{1}{{\mathrm{T}}_2}$

Consider the following statements regarding the network shown in the figure.

1. The equivalent resistance of the network between points A and Bis independent of value of G.
2. The equivalent resistance of the network between points A and B is $\frac{4}{3} \mathrm{R}$.
3. The current through G is zero.

Which of the above statements is/are true ?

• (1) alone

• (2) alone

• (2) and (3)

• (1), (2) and (3)

The torque required to hold a small circular coil of 10 turns, area 1 mm² and carrying a current of $\left(\frac{21}{44}\right)$ A in the middle of a long solenoid of 10³ turns/m carrying a current of 2.5 A, with its axis perpendicular to the axis of the solenoid is

• 1.5 × 10^-6 N-m

• 1.5 × 10^-8 N-m

• 1.5 × 10⁺⁶ N-m

• 1.5 × 10⁺⁸ N-m