﻿ An infinite line charge produces a field of 9 x 104 NC-1 at a

## Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

## Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.

# 21.An infinite line charge produces a field of 9 x 104 NC-1 at a distance of 2 cm. Calculate the linear charge density.

For infinite long line charge,

We have,

E = 9 x io4 N/C

r = 2 cm = 2 x 10-2 m

Hence,

1921 Views

22. Derive the expression for the energy stored in a capacitor of capacitance C, charged to a potential V.
1276 Views

23. A 100 W, 220 V bulb is connected to a 110 V dc source. Calculate the power consumed by the bulb.
185 Views

24. Derive an expression for the magnetic field at a point on the axis located at a distance ‘x’ from the centre of a magnetic dipole of length 21 and magnetic moment M.
189 Views

25.

An alternating emf of frequency 50 Hz is applied to a circuit with a resistor of 20 Ω, an inductor of 100 mH and a capacitor of 30 ηF connected in series.

(i) What is the angle by which the current leads or lags the applied emf ?

(ii) Represent the voltage and the current in a vector diagram showing the phase angle.

194 Views

26. PQ and MN are two parallel conductors at a distance I apart and connected by a resistance R as shown in figure 3. They are placed in a magnetic field B which is perpendicular to the plane of the conductors. A wire XY is placed over PQ and MN and then made to slide over PQ and MN with a velocity v.

Neglecting the resistance of PQ, MN and wire XY, calculate the work done per second to slide the wire XY.

363 Views

27. State Huygen’s principle in the wave theory of light. Using the principle, prove the laws of reflection of light.
763 Views

28. A lamp placed 50 cm from a screen on one side produces the same illumination as a standard 25 cd lamp placed 100 cm away on the other side of the screen. What is the luminous intensity of the first lamp ?
208 Views

29. If ‘d’ is the distance covered by a light wave in air in ‘t’ seconds and D’ is the distance covered in a medium of refractive index ‘n in the same time, prove that, d = nD.
214 Views

30. Determine the angular separation between the central maximum and the first order maximum of the diffraction pattern due to a single slit of width 0.25 mm when light of wavelength 5890 A is incident on it normally.
1022 Views