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Recent questions tagged medium

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

It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small flat search coil of area $2cm^2$ with closely wound turns, is positioned normal to the field direction and then quickly snatched out of the field region. Equivalently one can give it a quick $90^{\circ}$ turns to bring its plane parallel to the field direction. The total change flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5mc. The combined resistance of the coil and the galvanometer $0.50 \Omega$. Estimate the field strength of magnet.

asked Dec 30, 2016 by priyanka.c

1 answer

In p-n junction diode , the current I , can be expressed $I= I_0 exp \bigg[ \large\frac{eV}{K_{B}T}-1 \bigg]$ Where $I_0$ is called the satiation current , V is the voltage across the dicode and in positive for forward bias and negative for reverse bias and I is the current through the dicode , $K_B$ is the Boltzmann constant $(8.6 \times 10^{-5}e^v/k)$ and T is the absolute temperature . If for a given diode $I_0 = 5 \times 10^{-12}A $ and $T=300\;K$ , then what will be the increase in the current if the voltage across the diode is increased to $0.7\;A$?

asked Dec 30, 2016 by meena.p

1 answer

Give the expression for average value of a.c voltage $V = V_0\; sin \omega t$ over time interval $ t = 0 \; to \; t = \frac {\pi}{\omega}$

asked Dec 30, 2016 by suganyadevi.p

1 answer

An electrical element x connected to an alternating voltage source has current through it leading the voltage by $\frac {\pi}{2}$ radius. Identify x and write an expression for its reactance.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A pair of adjacent coils have a mutual inductance of 1.5 H. If the current in one is changed from $0 \; to\; 20 A$ is $0.5 S$ , what is the change of flux with the other coil.

asked Dec 30, 2016 by priyanka.c

1 answer

Self induction of an air core inductor increases from 0.01 MH to 10 MH on introducing an iron core into it. What is the relative permeability of the core used?

asked Dec 30, 2016 by suganyadevi.p

1 answer

Two amplifiers are connected one after the other in series (cascaded). The first amplifier has a voltage gain of $10$ and the second has a voltage gain of 20. If the input signal is $0.01\;V$ calculate the output a.c signal

asked Dec 30, 2016 by meena.p

1 answer

A magnetic field of 10T acts normal to a coil of 50 turns having $100 cm^2$ area. Find emf induced if the coil is removed from magnetic field in 0.1 sec.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A circular copper disc 10 cm in radius rotates at $20\pi$ rad/s about an axis through its centre and perpendicular to its disc. A uniform magnetic field of 0.2T acts perpendicular to the disc. Calculate the induced current if the resistance of the disc is $2\Omega$.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A circular copper disc 10 cm in radius rotates at $20\pi$ rad/s about an axis through its centre and perpendicular to its disc. A uniform magnetic field of 0.2T acts perpendicular to the disc. Calculate the potential difference developed between the axis of the disc and the rim.

asked Dec 30, 2016 by suganyadevi.p

1 answer

For a common emitter amplifier , the audio signal voltage across the collector resistance of $2\;HK \Omega$ is $2V$. Suppose the current amplification factor of a transistor is 100, find the input signal voltage and base current , if the base resistance is $1\;k \;\Omega$

asked Dec 30, 2016 by meena.p

1 answer

A circular coil of radius 8.0 cm and 20 turns rotates about its vertical diameter with an angular speed of $ 50 rad s^{-1}$ in a uniform horizontal magnetic field of magnitude $ 3 \times 10^{-2} T$. It the coil forms a closed loop of resistance $ 10 \Omega$, calculate the power dissipated as heat.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A circular coil of radius 8.0 cm and 20 turns rotates about its vertical diameter with an angular speed of 50 $rad s^{-1}$ in a uniform horizontal magnetic field of magnitude $ 3 \times 10^{-2} T$. Calculate the maximum emf induced in the coil.

asked Dec 30, 2016 by suganyadevi.p

1 answer

Why are resistance coils usually double wound?

asked Dec 30, 2016 by suganyadevi.p

1 answer

A magnetic field of flux density $1.0 wb m^{-2}$ acts normal to a 80 turn coil of 0.01 m^2 area. Find the e.m.f induced in it, if this coil is removed from the field in 0.1 second.

asked Dec 30, 2016 by suganyadevi.p

1 answer

Current in a circuit falls from $5.0 A$ to $0.0 A$ in $0.1 S$. If an average $emf$ of $ 200 V$ induced, given an estimate of the self-inductance of the circuit.

asked Dec 30, 2016 by priyanka.c

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

A wire of length 2m moves with a speed of 5 m/s perpendicular to a magnetic field of induction $0.1 wb/m^2$. The emf induced in the wire is

asked Dec 30, 2016 by suganyadevi.p

1 answer

A solenoid coil has 50 turns per cm along its length and a cross sectional area of $4cm^2$, 200 turns of another wire are wound round the first solenoid co-axially. The two coils are electrically insulated from each other. Calculate the mutual inductance between the two coils.

asked Dec 30, 2016 by suganyadevi.p

1 answer

Two coils have mutual inductance of 1.5 henry. If current in primary circuit is raised to 5 ampere in one millisecond after closing the circuit, what is the e.m.f induced in the secondary??

asked Dec 30, 2016 by suganyadevi.p

1 answer

An e.m.f of 250 microvolt in induced in a coil when current in it changes from 10A to 6A in 0.4 second. What is the self inductance of the coil?

asked Dec 30, 2016 by suganyadevi.p

1 answer

A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, where does the power come from ?

asked Dec 30, 2016 by priyanka.c

1 answer

The magnetic flex through a coil perpendicular to its plane and directed into paper is varying according to the relation $\phi = (5t^2 + 10t + 5)$ milliwebers. Calculate the e.m.f induced in the loop.

asked Dec 30, 2016 by suganyadevi.p

1 answer

An aircraft with a wingspan of 40m flies with a speed of 1080 $km hr^{-1}$ in the eastward direction at a constant altitude in the northern hemisphere where the vertical component of earth's magnetic field is $1.75 \times 10^{-5} T$. Find the emf that develops between the tips of the wings.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, calculate the average power loss due to Joule heating.

asked Dec 30, 2016 by priyanka.c

1 answer

A 12v battery connected to a $6 \Omega$, 10H coil through a switch drives a constant current in the circuit. Th switch is suddenly opened. Assuming that it took 1 millisecond to open the switch. Calculate the average e.m.f induced across the coil.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A $1.0m $ long metallic rod is rotated with an angular frequency of $400 rad/s$ about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of $0.5 \;T$ parallel to the axis exists everywhere. Calculate the $emf$ developed between the centre and the ring.

asked Dec 29, 2016 by priyanka.c

1 answer

A rectangular wire loop of slides $8 \;cm$ and $2\;cm$ with a small cut is moving out of a region of uniform field of magnitude $0.3T$ directed normal to the loop. What is the $emf$ developed across the cut if the velocity of the loop is $1\;cm/s$ in a direction normal to the shorter side of the loop. For how long does induced voltage last in each case.

asked Dec 29, 2016 by priyanka.c

1 answer

A long solenoid with $15\; turns\; per\; cm $ has a small loop of area $2.0cm^2$ placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from $2.0 A \; to \;4.0 A $ in $0.1 S ,$ what is the induced $emf$ in the loop while the current is changing?

asked Dec 29, 2016 by priyanka.c

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

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

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

A T.V tower has a height of 100 m , How much population is covered by the T.V broad cast if the average population density around the town is $5000 \;km^{-2}$?

asked Oct 3, 2016 by meena.p

1 answer

Compute the LC product of a tuned amplifier circuit which requires a carrier wave of $1\;MHz$ for amplitude modulation

asked Sep 30, 2016 by meena.p

1 answer

The maximum amplitude of an A.M wave is found to be $3\;v$ What is modulation index?

asked Sep 30, 2016 by meena.p

1 answer

Two waves A and B frequencies $2\;MHz$ and $3MHz$ respectively are beamed in the same direction for communication via sky wave .Which one of there is likely to travel longer distance in the ionosphere before suffering total internal reflection ?

asked Sep 30, 2016 by meena.p

2 answers

Would sky waves be suitable for transmission of TV signal of $60\; MHZ$ frequency ?

asked Sep 30, 2016 by meena.p

1 answer

A TV transmission tower has a height of $240 \;m$ signal broad cast from this will be received by LOS Communication at a distance of (assume the radius of earth to be $6.4 \times 10^6 \;m)$

asked Sep 30, 2016 by meena.p

1 answer

An audio signal of $15\;KHz$ , frequency can not be transmitted over long distances without modulation because

asked Sep 30, 2016 by meena.p

1 answer

A coil has an inductance of $5\;H$ and resistance $20\; \Omega$ . An emf of $100\; v$ is applied to it. What is the energy stored in the magnetic field, when the current has reached its final value .

asked Sep 28, 2016 by meena.p

1 answer

In a series LCR circuit , the voltage across an inductor, a capacitor and a resistor are $30\;v, 30\;v$ and $60\;v$ respectively . What is the phase difference between the applied voltage and the current in the circuit .

asked Sep 28, 2016 by meena.p

1 answer

A transformer has an efficiency of $80\%$ and works at 100 volt and 4 kw. If the secondary voltage is $240\;volt$ calculate the primary and secondary currents

asked Sep 27, 2016 by meena.p

1 answer

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