Recent questions tagged sec-c

What are the possible types of  pollinations in chasmogamous flowers. Give reasons.

asked Jun 13, 2017 by pady_1

1 answer

Are parthenocarpy and apomixes different phenomenon? Discuss their benefits.

asked Jun 13, 2017 by pady_1

1 answer

Vivipary automatically limits the number of offsprings in a litter. How?

asked Jun 13, 2017 by pady_1

1 answer

Given below are the events that are observed in an artificial hybridization programme. Arrange them

asked Jun 13, 2017 by pady_1

1 answer

Suggest a possible explanation why the seed in a pea pod are arranged in a row, whereas those in tom

asked Jun 12, 2017 by pady_1

1 answer

List the changes observed in an angiosperm flower subsequent to pollination and fertilization.

asked Jun 12, 2017 by pady_1

1 answer

List the changes observed in an angiosperm flower subsequent to pollination and fertilization.

asked Jun 12, 2017 by pady_1

1 answer

With which type of reproduction do we associate the reduction division ? Analyse the reasons for it.

asked Jun 12, 2017 by pady_1

1 answer

The number of texa exhibiting asexual reproduction is drastically reduced in higher plants (ang

asked Jun 12, 2017 by pady_1

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

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

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

A $600 \;pF$ capacitor is charged by a $200\; V$ supply. It is then disconnected from the supply and is connected to another uncharged $600 \;pF$ capacitor. How much electrostatic energy is lost in the process?

asked Jan 2, 2017 by meena.p

1 answer

If each diode in the figure has a forward bias resistance of $25\;\Omega$ and infinite resistance in reverse bias , What will be the values of the current $I_1, I_2, I_3$ and $I_4$ ?

asked Jan 2, 2017 by meena.p

1 answer

ODBAC is a fixed rectangular conductor of negligible resistance (co is not connected) and OP is a conductor which rotates clockwise with an angular velocity $w$ as shown in the fig. The entire system is in a uniform magnetic field B whose direction is along the normal to the surface of the rectangular conductor ABDC. The conductor OP is in electric contact with ABDC. The rotating conductor has resistance of X per unit length. Find the current in the rotating conductor as it rotates by $180^{\circ}$

asked Jan 1, 2017 by priyanka.c

1 answer

A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ . Is there a decrease in kinetic energy of XY equalling the heat lost in R ?

asked Jan 1, 2017 by priyanka.c

1 answer

A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ If B is independent of time, obtain $V (t)$ assuming $V(0) = u_0$

asked Jan 1, 2017 by priyanka.c

1 answer

A magnetic field $B =B_o \sin(wt) \hat{k}$ covers a large region where a wire AB slides smoothly over two parallel conductors separated by a distance d, as shown in the fig. The wire are in the x-y plane. The wire AB (of length d) has resistance R and the parallel wires have negligible resistance. It AB is moving velocity $v$, what is the force needed to keep the wire at constant velocity ?

asked Jan 1, 2017 by priyanka.c

1 answer

A conducting wire XY of mass $m$ and negligible resistance slides smoothly on two parallel conducting wire as shown in the fig. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field $B = B (+) \hat {k}$ write down the equation for the acceleration of the wire XY.

asked Jan 1, 2017 by priyanka.c

1 answer

Obtain an expression for the mutual inductance between a long straight wire and a square of side a as shown in the figure .

asked Dec 31, 2016 by priyanka.c

1 answer

An air-cored solenoid with length 30cm, area of cross section $25 cm^2$ and number of turns 500, carries a current of 2.5A. The current is suddenly switched off in a brief time of $10^{-3}S.$ How much is the average back emf induced across the ends of the open switch in the circuit ? Ignore the variation in magnetic field near the ends of the solenoid ?

asked Dec 31, 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 BoHZmann 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 $0.7\;A$?what will be the Dynamic resistance

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

A square loop of side 12cm with its sides parallel to X and Y axes is moved with a velocity of 8 cm/s in the positive X-direction in an environment containing a magnetic field in the positive Z-direction. The field is neither uniform in space nor constant in time. It has a gradient of $10^{-3}$T/cm along the negative X-direction (that is it increases by $10^{-3}$T/cm as one moves in the negative X-direction) and it is decreasing in time at the rate of $10^{-3} $ T/S. Determine the direction and magnitude of the induced current in the loop if its resistance is $4.50 m\Omega$

asked Dec 30, 2016 by priyanka.c

1 answer

Suppose a rectangular loop of sides 8cm and 2cm with a small cut is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initial value of 0.3T at the rate of 0.02T/S. If the cut is joined and the loop has a resistance of 1.6$ \Omega$, how much power is dissipated by the loop as heat? What is the source of this power ?

asked Dec 30, 2016 by priyanka.c

1 answer

A magnetic field in a certain region is given by $ B = B_0 cm (\omega t) \hat {k}$ and a coil of radius "a" with resistance R is placed in the x - y plane with its centre at the origin in the magnetic field, as shown in the fig. Find the magnitude and th direction of the current at (a, 0, 0) at $ t = \frac {\pi}{2\omega} \; and \; t = \frac {3 \pi}{2 \omega}$

asked Dec 30, 2016 by suganyadevi.p

1 answer

A rectangular loop of wire ABCD is kept close to an infinitely long wire carrying a current $ I (t) = I_0 (1 - \frac {t}{T}) for $ 0 \leq t \leq T$ and $ I (0) = 0$ for t > T, as shown in the fig. Find the total charge passing through a given point in the loop, in time T, The resistance of the loop is R.

asked Dec 30, 2016 by suganyadevi.p

1 answer

Consider an infinitely long wire carrying a current I(t), with $ \frac {dI}{dt} = \lambda = constant$. Find the current produced in the rectangular loop of wire ABCD if its resistance is R, as shown in the fig.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A magnetic field B is confined to a region $r \leq a$ and points out the paper (the Z axis) $ r = 0$ being the centre of the circular region. A charged ring (charge = Q) of radius b $b>a$ and mass m lies in the xy plane with its centre at the origin. the ring is free to rotate and is at rest. The magnetic field is brought to zero in time $\bigtriangleup t$. Find the angular velocity $\omega$ of the ring after the field vanister.

asked Dec 30, 2016 by suganyadevi.p

1 answer

A jet plane is travelling towards west at a speed of $1800\; km/hr$. What is the voltage difference developed between the ends of the wing having a span of 25m, if the earth's magnetic field at the location has a magnitude of $5 \times 10^{-4} T$ and the dip angle is $30^{\circ}$

asked Dec 30, 2016 by priyanka.c

1 answer

A conducting circular loop is placed in a uniform magnetic field B = 0.020 T with its plane perpendicular to the field. The radius of the loop starts shrinking at a constant rate of 1.0 mm/s. Find the induced e.m.f in the loop at an instant when the radius is 2cm?

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

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 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 maximum value of current in the coil.

asked Dec 29, 2016 by priyanka.c

1 answer

Ask Questions, Get Answers