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Questions >> JEEMAIN and NEET >> Physics >> Class12

Class12

Electric Charges and Fields

Electrostatic Potential and Capacitance

Current Electricity

Moving Charges and Magentism

Magnetism and Matter

Electromagnetic Induction

Alternating Current

Electromagnetic Waves

Ray Optics and Optical Instruments

Dual Nature of Matter and Radiation

Semiconductor Materials and Electronic Devices

Communication Systems

Experimental Skills in Physics

Three capacitors, each of capacitance C are connected to a battery of voltage V. When key K is closed, the charge which will flow through the battery is (see figure).

asked Mar 22, 2018 by guptakanishq1

1 answer

Six charges are placed at the vertices of a rectangular hexagon as shown in fig. The electric field on the line passing through point O and perpendicular to the plane of the figure as a function of X from point O is (x>>>a)

asked Aug 1, 2015 by _1

1 answer

a body dropped freely from a height h on to a horizontal plane, bounces up and down and finally comes to rest. the coefficient of restitution is e. the ratio of velocities at the beginning and after two rebounds is

asked Jul 28, 2015 by excellentdeals18

1 answer

force of interaction between two axial short electric dipoles whose centres are R distance apart varies as

asked May 9, 2015 by sapnakatyal27

1 answer

electric charge Q,Q and -2Q resp. are placed at the three corners of an equilateral triangle of side a . magnitude of the elctrical dipole moment of the system is

asked May 9, 2015 by sapnakatyal27

2 answers

find out the value of d as shown in fig.

asked Dec 12, 2014 by vishavjeetmor

1 answer

Selenium (Se) is a group VI element (i.e. two columns to the right of Silicon on the periodic table). An extrinsic semiconductor is produced by doping Silicon (Si) with 1020 Selenium atoms per m3. Assuming saturation, calculate the conductivity of the extrinsic semiconductor.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Given $n_i = 2.4 \times 10^{19} m^{-3}, \; \mu_n = 0.39\;m^2/V.S, \; \mu_p = 0.19\;m^2/V.s$ for intrinsic Ge at room temperature of $300^{\circ}\;K$ , calculate the conductivity of the sample.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Estimate the conductivity ( $\sigma_i$ ) and resistivity ( $\rho_i$ ) of silicon atoms and electron-hole pairs at room temperature of $300^{\circ}\;K$ if every 10-millionth silicon atom is replaced by an atom of Indium.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Estimate the intrinsic conductivity ( $\sigma_i$ ) and resistivity ( $\rho_i$ ) of silicon atoms and electron-hole pairs at room temperature of $300^{\circ}\;K$ .

asked Jul 13, 2014 by balaji.thirumalai

1 answer

C, Si and Ge atoms have 4 Valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by $E_C, E_{Si}, E_{Ge}$ respectively. Which of the following relationship is true in their case?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Which of the following statements about intrinsic semiconductors are incorrect?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Suppose a pure Si crystal has $5 \times 10^{28} \text{atoms} / m^3$ . It is doped by 1 ppm concentration of pentavalent As. Calculate the number of electrons and holes, given that $n_i = 1.5 \times 10^{16} \;/m^3$

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A semiconductor has an electron concentration of $0.45 \times 10^{22} \; /m^3$ and a hole concentration of $5 \times 10^{20} \;/ m^3$ . Find its conductivity.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A p type semiconductor has acceptor level of 57 mev above the valance band. Find the maximum wave length of light which can create a hole.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Given that logic Gates can be represented as Venn Diagrams, match the following:

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Evaluate the correct Boolean Expression for the given circuit?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Evaluate the correct Boolean Expression for the given circuit?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Evaluate the correct Boolean Expression for the given circuit?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Match the following for a FM Wave:

asked Jul 13, 2014 by balaji.thirumalai

1 answer

What are the minimum and maximum Amplitude of an AM wave represented by the expression: $v = 5(1+0.6\cos 6280 t) \sin 211 \times 10^4 \; \text{volts}$ ?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

What are the three frequencies of an AM wave represented by the expression: $v = 5(1+0.6\cos 6280 t) \sin 211 \times 10^4 \; \text{volts}$ ?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

An AM signal is represented by the equation $25+5\sin (2\pi\times 8\times 10^3\;t) \times \sin (2\pi\times 0.25\times10^6\;t)$ . Calculate the bandwidth, the modulating factor and the amplitude of each side frequency?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

An AM signal is represented by the equation $10+4\sin (2\pi\times 3\times 10^3\;t) \times \sin (2\pi\times 0.3\times10^6\;t)$ . Calculate the bandwidth, the modulating factor and the amplitude of each side frequency?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmission tower at a particular place has a height of 135m. (A) What is its coverage range? (B) By how much should the height be increased to 2 times its coverage range? Given that radius of earth = 6400 km.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmission tower at a particular place has a height of 200m. (A) What is its coverage range? (B) By how much should the height be increased to 1.4 times its coverage range? Given that radius of earth = 6400 km.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmission tower at a particular place has a height of 150m. (A) What is its coverage range? (B) By how much should the height be increased to 1.2 times its coverage range? Given that radius of earth = 6400 km.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmission tower at a particular place has a height of 176m. (A) What is its coverage range? (B) By how much should the height be increased to 1.25 times its coverage range? Given that radius of earth = 6400 km.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 24 Watts of 43% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 40 Watts of 30% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 40 Watts of 30% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 15 Watts of 16% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 32 Watts of 28% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

A transmitter puts out a total power of 25 Watts of 30% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

An AM signal is represented by the equation $15+3\sin (2\pi\times 5\times 10^3\;t) \times \sin (2\pi\times 0.5\times10^6\;t)$ . What is the amplitude of each side frequency?

asked Jul 12, 2014 by balaji.thirumalai

1 answer

When 80% AM is transmitted total power is 10kW. What is the power saved if the carrier and one side band are suppressed?

asked Jul 12, 2014 by balaji.thirumalai

1 answer

A standard AM broadcast station is allowed to transmit modulating frequencies up to 5 kHz. If the AM station is transmitting on a frequency of 980 kHz, what is the total bandwidth occupied by the AM station?

asked Jul 12, 2014 by balaji.thirumalai

1 answer

If the maximum peak-to-peak voltage of an AM wave is 16mV and the minimum peak-to peak voltage is 4mV, calculate the modulation factor.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

A transmission tower at a particular place has a height of 160m. (A) What is its coverage range? (B) By how much should the height be increased to double its coverage range? Given that radius of earth = 6400 km.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

A message signal of frequency 12 kHz and peak voltage of 20 volts is used to modulate a carrier of frequency 12 MHz and peak voltage of 30 volts. Determine (a) modulation index, (b) the side bands produced and (c) bandwidth of modulated wave.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

A message signal of frequency 10 kHz and peak voltage of 10 volts is used to modulate a carrier of frequency 1 MHz and peak voltage of 20 volts. Determine (a) modulation index, (b) the side bands produced.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

A transmitting antenna at the top of a tower has a height 32 m and the height of the receiving antenna is 50 m. What is the maximum distance between them for satisfactory communication in LOS mode? Given radius of earth 6.4 $\times$ 106 m.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

The refractive indices of flint glass for red and violet light are 1.613 and 1.632 respectively. Find the angular dispersion produced by a thin prism of flint glass having refracting angle $15 ^{\circ}$

asked Apr 19, 2014 by balaji.thirumalai

1 answer

In a Young's Double Slit experiment, the width of one of the two slits is double the other. If the amplitude of light coming from a slit is proportional to the width, find the ratio of the maximum to minimum intensity in the interference pattern.

asked Apr 19, 2014 by balaji.thirumalai

1 answer

Two monochromatic coherent sources of wavelength 5000 A are placed along line normal to screen as shown. Find the order of central bright fringe if $d = 0.5mm$ and $D = 1m$

asked Apr 19, 2014 by balaji.thirumalai

1 answer

Figure shows a capacitor made of two circular plates each of radius $12\: cm$ , and separated by $5\: cm$ . The capacitor is being charged by an external source. The charging current is constant and equal to $0.15\: A$ . The rate of change in potential difference between the plates is

asked Apr 3, 2014 by balaji.thirumalai

1 answer

The main scale of a vernier calipers reads in millimeter and its vernier scale is divided into 10 divisions which coincide with 9 divisions of the main scale. When the two jaws of the instrument touch each other the seventh division of the vernier scale coincide with a scale division and the zero of the vernier lies to the right of the zero of the main scale. Furthermore, when the cylinder is tightly placed along its length between the two jaws, the zero of the vernier sale lies slightly to the left of 3.2 cm; and the fourth vernier division coincides with a scale division. What will the measured length of the cylinder be?

asked Apr 2, 2014 by balaji.thirumalai

1 answer

If $L= 10\;mH,C=100\;\mu F,R=100 \;\Omega$ in a LCR circuit the value of resonance frequency is

asked Mar 27, 2014 by meena.p

1 answer

Power factor of resonance LCR circuit is

asked Mar 27, 2014 by meena.p

1 answer

In an ac circuit $E=E_0\;\sin wt$ and $I=I_0 \sin (wt -\large\frac{\pi}{2})$ the power consumption in circuit is

asked Mar 27, 2014 by meena.p

1 answer

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