Recent questions tagged additional

A parallel plate capacitor with air between the plates has a capacitance of $8\;pF$ . The separation between the plates is now reduced by half and the space between them is filled with a medium of dielectric constant 5. Calculate the value of capacitance of the capacitor in the second case .

asked Jan 3, 2017 by meena.p

1 answer

Two charges $2\mu C$ and $-2 \mu C$ are placed at points A and B, 5cm apart . Depict an equipotential surface of the system

asked Jan 3, 2017 by meena.p

1 answer

An electrical technician requires a capacitance of $2 \mu F$ in a circuit across a potential difference of $1\; kV$. A large number of $1\; \mu F$ capacitors are available to him each of which can withstand a potential difference of not more than $400\; V$. Suggest a possible arrangement that requires the minimum number of capacitors.

asked Jan 3, 2017 by meena.p

1 answer

A spherical capacitor consists of two concentric spherical conductors, where outer and inner radii are $r_1$ and $r_2$ respectively as shown in the figure.The capacitance of the spherical capacitor is

asked Jan 3, 2017 by meena.p

1 answer

Calculate the potential at a point P due to a charge of $4 × 10^{–7}\;C$ located $9\; cm$ away.

asked Jan 3, 2017 by meena.p

1 answer

Two charged conducting spheres of radii a and b are connected to each other by a wire. What is the ratio of electric fields at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of a conductor is higher than on its flatter portions.

asked Jan 3, 2017 by meena.p

1 answer

In a hydrogen atom, the electron and proton are bound at a distance of about $0.53 \dot{A}$: What is the minimum work required to free the electron, given that its kinetic energy in the orbit is half the magnitude of potential energy obtained ?

asked Jan 2, 2017 by meena.p

1 answer

In a hydrogen atom, the electron and proton are bound at a distance of about 0.53 Å: Estimate the potential energy of the system in eV, taking the zero of the potential energy at infinite separation of the electron from proton.

asked Jan 2, 2017 by meena.p

1 answer

A spherical conducting shell of inner radius $r_1$ and outer radius $r_2$ has a charge Q. Is the electric field inside a cavity (with no charge) zero, even if the shell is not spherical, but has any irregular shape? Explain.

asked Jan 2, 2017 by meena.p

1 answer

The plates of a parallel plate capacitor have an area of $90\; cm^2$ each and are separated by $2.5\; mm$. The capacitor is charged by connecting it to a $400\; V$ supply.How much electrostatic energy is stored by the capacitor?

asked Jan 2, 2017 by meena.p

1 answer

A $4 \mu F$ capacitor is charged by a $200\; V$ supply. It is then disconnected from the supply, and is connected to another uncharged $2 \mu F$ capacitor. How much electrostatic energy of the first capacitor is lost in the form of heat and electromagnetic radiation?

asked Jan 2, 2017 by meena.p

1 answer

A spherical capacitor has an inner sphere of radius 12 cm and an outer sphere of radius 13 cm. The outer sphere is earthed and the inner sphere is given a charge of $2.5 \mu C$. The space between the concentric spheres is filled with a liquid of dielectric constant $32$. What is the potential of the inner sphere?

asked Jan 2, 2017 by meena.p

1 answer

A spherical capacitor has an inner sphere of radius 12 cm and an outer sphere of radius 13 cm. The outer sphere is earthed and the inner sphere is given a charge of $2.5 \mu C$. The space between the concentric spheres is filled with a liquid of dielectric constant $32$. Determine the capacitance of the capacitor.

asked Jan 2, 2017 by meena.p

1 answer

A cylindrical capacitor has two co-axial cylinders of length $15\; cm$ and radii $1.5\; cm$ and $1.4\; cm$. The outer cylinder is earthed and the inner cylinder is given a charge of $3.5\; \mu C$. Determine the capacitance of the system and the potential of the inner cylinder. Neglect end effects (i.e., bending of field lines at the ends).

asked Jan 2, 2017 by meena.p

1 answer

A parallel plate capacitor is to be designed with a voltage rating $1\; kV$, using a material of dielectric constant $3$ and dielectric strength about $10^7\; Vm^{−1}$. (Dielectric strength is the maximum electric field a material can tolerate without breakdown, i.e., without starting to conduct electricity through partial ionisation.) For safety, we should like the field never to exceed, say $10 \%$ of the dielectric strength. What minimum area of the plates is required to have a capacitance of $50\; pF$?

asked Jan 2, 2017 by meena.p

1 answer

In a Van de Graaff type generator a spherical metal shell is to be a $15 × 10^6\; V$ electrode. The dielectric strength of the gas surrounding the electrode is $5 × 10^7 \;Vm^{−1}$. What is the minimum radius of the spherical shell required?

asked Jan 2, 2017 by meena.p

1 answer

A small sphere of radius $r_1$ and charge $q_1$ is enclosed by a spherical shell of radius $r_2$ and charge $q_2$. Show that if $q_1$ is positive, charge will necessarily flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge $q_2$ on the shell is.

asked Jan 2, 2017 by meena.p

1 answer

A spherical conductor of radius $12\; cm$ has a charge of $1.6 \times 10^{−7}\;C$ distributed uniformly on its surface. What is the electric field at a point 18 cm from the center of the sphere ?

asked Jan 2, 2017 by meena.p

1 answer

A spherical conductor of radius $12\; cm$ has a charge of $1.6 \times 10^{−7}\;C$ distributed uniformly on its surface. What is the electric field just outside the sphere ?

asked Jan 2, 2017 by meena.p

1 answer

A spherical conductor of radius $12\; cm$ has a charge of $1.6 \times 10^{−7}\;C$ distributed uniformly on its surface. What is the electric field inside the sphere ?

asked Jan 2, 2017 by meena.p

1 answer

A charge of $8\; mC$ is located at the origin. Calculate the work done in taking a small charge of $−2 \times 10^{−9}\; C$ from a point $P (0, 0, 3 \;cm)$ to a point $Q (0, 4 \;cm, 0)$, via a point $R (0, 6cm, 9 cm)$.

asked Jan 2, 2017 by meena.p

1 answer

A p-n photo diode is fabricated from a semi - conductor with a band gap of $2.5 \;ev$. It can detect a signal of wavelength

asked Dec 31, 2016 by meena.p

1 answer

The voltage gain of an amplifier with $9\%$ negative feed back is $10$. The voltage gain with out feedback will be

asked Dec 31, 2016 by meena.p

1 answer

The decimal equivalent of the binary number $(11010.101)_2$ is

asked Dec 31, 2016 by meena.p

1 answer

An amplifier has a voltage gain $A_v= 1000$ The voltage gain $dB$ is

asked Dec 31, 2016 by meena.p

1 answer

In a common emitter configuration, a transistor has $\beta=50$ and input resistance is $1 \;k \Omega$ If the peak value of a.c input is $0.01\;v$, then the peak value of collector currrent is

asked Dec 31, 2016 by meena.p

1 answer

In a common emitter transistor amplifier , the output resistance is $500 \;k \Omega$ and the current gain $\beta =49$ . If the power gain of the amplifier is $5 \times 10^6$, the input resistance is

asked Dec 31, 2016 by meena.p

1 answer

A junction diode has a resistance of $25 \Omega$ when forward biased and $2500\;\Omega$ when reverse biased . The current in the diode for arrangement will be

asked Dec 31, 2016 by meena.p

1 answer

In a transistor $\beta=49$ , then what percentage of charge carriers from emitter reach the collector ?

asked Dec 31, 2016 by meena.p

1 answer

A semiconductor has equal electron and hole concentration $6 \times 10^8\;m^{-3}$. On doping with a certain impurity , electrons concentration increases to $8 \times 10^{12}m^{-3}$. Identify the type of semiconductor after doping

asked Dec 31, 2016 by meena.p

1 answer

What is the order of energy gap in a semi-conductor ?

asked Dec 31, 2016 by meena.p

1 answer

give the ratio of number of numbers holes and number of conduction electrons in an intrinsic semi conductor

asked Dec 31, 2016 by meena.p

1 answer

A cylindrical bar magnet is kept along the axis of a circular coil and near it as shown in the fig. Will there be any induced e.m.f at the terminals of the coil, when the magnet is rotated about an axis perpendicular to the length of the magnet?

asked Dec 30, 2016 by suganyadevi.p

1 answer

The magnetic flux linked with a coil is $ \phi = (3t^2 - 2t + 1) $milli weber. The e.m.f induced in the coil at t = 1 sec is:

asked Dec 30, 2016 by suganyadevi.p

1 answer

An AM transmitter records an antenna current of $10.5\;A$ . The antenna current drops to $10\;A$ when only carrier is transmitted. What is the percentage modulation ?

asked Oct 3, 2016 by meena.p

1 answer

When a broad cast AM transmitter is $50\%$ modulated its antenna current is $12\;A$ . What would be the carrier current ?

asked Oct 3, 2016 by meena.p

1 answer

If $V_r$ is velocity of red light and $V_b$ is the velocity of blue light in vacuum, then

asked Oct 3, 2016 by meena.p

1 answer

The TV transmission tower in Delhi has a height of $340\;m$ . The distance up to which the broad cost can received , (taking the radius of earth to be $6.4 \times 10^{6}m)$ is

asked Oct 3, 2016 by meena.p

1 answer

Refractive index of ionosphere is

asked Oct 3, 2016 by meena.p

1 answer

The electro magnetic waves of frequency $2\; MHz$ to $30\;MHz$ are used

asked Oct 3, 2016 by meena.p

1 answer

Which of the following frequencies will be suitable for beyond the horizon communication ?

asked Oct 3, 2016 by meena.p

1 answer

A radio station has two channels . One is AM at $1020\;KHz$ and the other FM at $89.5\;MHZ$ For good result you will use

asked Oct 3, 2016 by meena.p

1 answer

LANDSAT series of satellite move in near polar orbits at an attitude of

asked Oct 3, 2016 by meena.p

1 answer

The sky wave with a frequency of $50\;MHz$ is incident on D- region at an angle of $30^{\circ}$ then angle of refraction is

asked Oct 3, 2016 by meena.p

1 answer

When radio waves passes through ionosphere , phase difference between space current and captive displacement current is .

asked Oct 3, 2016 by meena.p

1 answer

Modem is a device which perform

asked Oct 3, 2016 by meena.p

1 answer

Calculate the phase velocity of electro magnetic wave having electron density and frequency for D layer , $N = 400\; electron /cc, \nu = 300\;kHz$

asked Oct 3, 2016 by meena.p

1 answer

The maximum range of ground or surface wave propagation depends on

asked Oct 3, 2016 by meena.p

1 answer

Calculate the length of half wave dipole antenna at $300\;MHz$

asked Oct 3, 2016 by meena.p

1 answer

A 400 watt carrier is modulated to a depth of $75\%$ . calculate the total power in the modulated wave .

asked Oct 3, 2016 by meena.p

1 answer

Ask Questions, Get Answers