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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 2601. |
The average electric field of electromagnetic waves in certain region of free space is\[9\times {{10}^{-4}}N{{C}^{-1}}\]. Then the average magnetic field in the same region is of the order of |
| A. | \[27\times {{10}^{-4}}T\] |
| B. | \[3\times {{10}^{-12}}T\] |
| C. | \[\left( \frac{1}{3} \right)\times {{10}^{-12}}T\] |
| D. | \[3\times {{10}^{-12}}T\] |
| Answer» C. \[\left( \frac{1}{3} \right)\times {{10}^{-12}}T\] | |
| 2602. |
A plane electromagnetic wave travels in free space along X-direction. If the value of \[\vec{B}\] (in tesla) at a particular point in space and time is\[1.2\times {{10}^{-8}}\hat{k}\]. The value of \[\vec{E}\] (in \[V{{m}^{-1}}\]) at that point is |
| A. | \[1.\,2\text{ }\hat{j}\] |
| B. | \[3.\,6\,\hat{k}\] |
| C. | \[1.\,2\,\hat{k}\] |
| D. | \[3.\,6\hat{j}\] |
| Answer» E. | |
| 2603. |
The wave impendance of free space is |
| A. | zero |
| B. | \[376.6\Omega \] |
| C. | \[33.66\Omega \] |
| D. | \[3.76\Omega \] |
| Answer» C. \[33.66\Omega \] | |
| 2604. |
If a source is transmitting electromagnetic wave of frequency \[8.2\times {{10}^{6}}Hz,\] then wavelength of the electromagnetic waves transmitted from the source will be |
| A. | \[36.6\,m\] |
| B. | \[40.5\,m\] |
| C. | \[42.3\,m\] |
| D. | \[50.9\,m\] |
| Answer» B. \[40.5\,m\] | |
| 2605. |
In a wave \[{{E}_{0}}=100\,V{{m}^{-1}}\]. Find the magnitude of Pointing?s vector |
| A. | \[13.25\text{ }W{{m}^{-2}}\] |
| B. | \[26.5\text{ }W{{m}^{-2}}\] |
| C. | \[18.25\text{ }W{{m}^{-2}}\] |
| D. | \[19.7\text{ }W{{m}^{-2}}\] |
| Answer» C. \[18.25\text{ }W{{m}^{-2}}\] | |
| 2606. |
The figure shows graphs of the electric field magnitude E versus time t for four uniform electric fields, all contained within identical circular regions. Which of them is according to the magnitudes of the magnetic field? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 2607. |
An electromagnetic wave of frequency \[v=3.0\text{ }MHz\] passes from vacuum into a dielectric medium with permittivity \[\in \,=4.0\]. Then |
| A. | wavelength is halved and frequency remains unchanged |
| B. | wavelength is doubled and frequency becomes half |
| C. | wavelength is doubled and the frequency remains unchanged |
| D. | wavelength and frequency both remain unchanged. |
| Answer» B. wavelength is doubled and frequency becomes half | |
| 2608. |
The magnetic field between the plates of radius 12 cm separated by distance of 4 mm of a parallel plate capacitor of capacitance \[100\text{ }pF\] along the axis of plates having conduction current of \[0.15A\] is |
| A. | zero |
| B. | \[1.5\,T\] |
| C. | \[15\,T\] |
| D. | \[0.15\,T\] |
| Answer» B. \[1.5\,T\] | |
| 2609. |
Consider an electromagnetic wave propagating in vacuum. Choose the correct statement: |
| A. | For an electromagnetic wave propagating in \[+y\] direction the electric field is \[\vec{E}=\frac{1}{\sqrt{2}}{{E}_{yz}}\,(x,t)\,\hat{z}\] and the magnetic field is \[\overrightarrow{B}=\frac{1}{\sqrt{2}}{{B}_{z}}(x,t)\hat{y}\] |
| B. | For an electromagnetic wave propagating in \[+y\] direction the electric field is \[\vec{E}=\frac{1}{\sqrt{2}}{{E}_{yz}}(x,t)\,\hat{z}\] and the magnetic field is \[\vec{B}=\frac{1}{\sqrt{2}}{{B}_{yz}}(x,t)\,\hat{y}\] |
| C. | For an electromagnetic wave propagating in \[+x\] direction the electric field is \[\vec{E}=\frac{1}{\sqrt{2}}{{E}_{yz}}\,(y,\,\,z,\,\,t)\] \[\left( \hat{y}+\hat{z} \right)\] and the magnetic field is \[\vec{B}=\frac{1}{\sqrt{2}}{{B}_{yz}}\,(y,\,\,z,\,\,t)\,(\hat{y}+\hat{z})\] |
| D. | For an electromagnetic wave propagating in \[+x\] direction the electric field is \[\vec{E}=\frac{1}{\sqrt{2}}{{E}_{yz}}\,(x,t)\,\left( \hat{y}-\hat{z} \right)\]and the magnetic field is \[\vec{B}=\frac{1}{\sqrt{2}}{{B}_{yz}}\,(x,t)\,\left( \hat{y}+\hat{z} \right)\] |
| Answer» E. | |
| 2610. |
An electromagnetic wave with frequency cd and wavelength \[\lambda \] travels in the \[+y\] direction. Its magnetic field is along + x-axis. The vector equation for the associated electric field (of amplitude \[{{E}_{0}}\]) is |
| A. | \[\overset{\to }{\mathop{E}}\,=-{{E}_{0}}\cos \left( \omega t+\frac{2\pi }{\lambda }y \right)\hat{x}\] |
| B. | \[\overset{\to }{\mathop{E}}\,={{E}_{0}}\cos \left( \omega t-\frac{2\pi }{\lambda }y \right)\hat{x}\] |
| C. | \[\overset{\to }{\mathop{E}}\,={{E}_{0}}\cos \left( \omega t-\frac{2\pi }{\lambda }y \right)\hat{z}\] |
| D. | \[\overset{\to }{\mathop{E}}\,=-{{E}_{0}}\cos \left( \omega t+\frac{2\pi }{\lambda }y \right)\hat{z}\] |
| Answer» D. \[\overset{\to }{\mathop{E}}\,=-{{E}_{0}}\cos \left( \omega t+\frac{2\pi }{\lambda }y \right)\hat{z}\] | |
| 2611. |
In a plane electromagnetic wave propagating in space has an electric field of amplitude \[9\times {{10}^{3}}V/m\] then the amplitude of the magnetic field is |
| A. | \[2.7\times {{10}^{12}}T\] |
| B. | \[9.0\times {{10}^{-3}}T\] |
| C. | \[3.0\times {{10}^{-4}}T\] |
| D. | \[3.0\times {{10}^{-5}}T\] |
| Answer» E. | |
| 2612. |
For wave propagation of a \[10\text{ }MHz\] signal, what should be the maximum electron density in ionosphere |
| A. | \[\tilde{\ }1.2\times {{10}^{12}}{{m}^{-3}}\] |
| B. | \[\tilde{\ }{{10}^{6}}{{m}^{-3}}\] |
| C. | \[\tilde{\ }{{10}^{14}}{{m}^{-3}}\] |
| D. | \[\tilde{\ }{{10}^{22}}{{m}^{-3}}\] |
| Answer» B. \[\tilde{\ }{{10}^{6}}{{m}^{-3}}\] | |
| 2613. |
A point source of electromagnetic radiation has an average power output of 800 W. The maximum value of electric field at a distance \[4.0\text{ }m\] from the source is |
| A. | \[64.7\text{ }V/m\] |
| B. | \[57.8\text{ }V/m\] |
| C. | \[56.72\text{ }V/m\] |
| D. | \[54.77\text{ }V/m\] |
| Answer» E. | |
| 2614. |
In an electromagnetic wave, the electric and magnetic fields are \[100\,V{{m}^{-1}}\] and \[0.265\,A\,{{m}^{-1}}\]. The maximum energy flow is |
| A. | \[26.5\text{ }W/{{m}^{2}}\] |
| B. | \[36.5\text{ }W/{{m}^{2}}\] |
| C. | \[46.7\text{ }W/{{m}^{2}}\] |
| D. | \[765\text{ }W/{{m}^{2}}\] |
| Answer» B. \[36.5\text{ }W/{{m}^{2}}\] | |
| 2615. |
In a conducting cycle wheel (of n spokes), each spoke of length fi is rotating with angular speed \[\omega \] in uniform perpendicular magnetic field B. If due to flux cutting each metal spoke behaves as an identical cell of emf(e) then net emf of the system is |
| A. | \[nB\omega {{l}^{2}}\] |
| B. | \[\frac{1}{2}nB\omega {{l}^{2}}\] |
| C. | \[\frac{1}{2}B\omega {{l}^{2}}\] |
| D. | \[B\omega {{l}^{2}}\] |
| Answer» D. \[B\omega {{l}^{2}}\] | |
| 2616. |
The incorrect statements is/are |
| A. | The resistance offered by an inductor in a d. c circuit is always constant. |
| B. | The resistance of inductor in steady state is zero. |
| C. | An inductor is connected to a battery through a switch. The emf induced in the inductor is much larger when the switch is opened as compared to the emf induced when the switch is closed. |
| D. | To reduce the rate of increases of current through a solenoid should increase the time constant\[\left( \frac{L}{R} \right)\]. |
| Answer» B. The resistance of inductor in steady state is zero. | |
| 2617. |
A (current versus time) graph of the current passing through a solenoid is shown in figure. If the back emf at t=3s is e, find the back emf at t = 7 s |
| A. | \[e/2\] |
| B. | 0 |
| C. | \[\frac{-e}{2}\] |
| D. | \[-3e\] |
| Answer» E. | |
| 2618. |
A metal rod moves at a constant velocity in a direction perpendicular to its length. A constant, uniform magnetic field exists in space in a direction perpendicular to the rod as well as its velocity. Select the correct statement from the following. |
| A. | The entire rod is at the same electric potential. |
| B. | There is an electric field in the rod. |
| C. | The electric potential is highest at the centre of the rod and decreases towards its ends. |
| D. | The electric potential is lowest at the centre of the rod, and increases towards its ends |
| Answer» C. The electric potential is highest at the centre of the rod and decreases towards its ends. | |
| 2619. |
A uniform circular loop of radius a and resistance R is placed perpendicular to a uniform magnetic field B. One half of the loop is rotated about the diameter with angular velocity\[\omega \]as shown in Fig. Then, the current in the loop is |
| A. | \[\frac{\pi {{a}^{2}}B\omega }{4R}\], when \[\theta \] is zero |
| B. | \[\frac{\pi {{a}^{2}}B\omega }{2R}\], when \[\theta \] is zero |
| C. | zero, when \[\theta =\pi /2\] |
| D. | \[\frac{\pi {{a}^{2}}B\omega }{2R}\], when \[\theta =\pi /2\] |
| Answer» E. | |
| 2620. |
The magnetic flux \[\phi \] linked with a conducting coil depends on time as \[\phi =4{{t}^{n}}+6\], where n is a positive constant. The induced emf in the coil is e. Then which is wrong? |
| A. | If \[0<n<1\], \[e\ne 0\] and \[\left. \left| e \right. \right|\]decreases with time |
| B. | If n=1, e is constant |
| C. | If n > 1, \[\left| e \right|\]increases with time |
| D. | If n>l, \[\left| e \right|\] decreases with time |
| Answer» E. | |
| 2621. |
ABCD is a wire frame in the shape of an isosceles trapezium (i.e., length AB = length CD) enter a magnetic field with flux density B at t=0 as shown in the figure. If the total resistance of wire frame is R. What is the value of the induced current in the wire frame after t seconds, assuming that the frame has to entered the field completely by then? [v=Velocity of frame] |
| A. | zero |
| B. | \[\frac{Bv}{R}(2vt\,\sin \,\theta +\ell )\] |
| C. | \[\frac{Bv}{R}\left( \frac{2vt\,}{\tan \,\theta }+\ell \right)\] |
| D. | \[\frac{B}{v}\] |
| Answer» D. \[\frac{B}{v}\] | |
| 2622. |
An infinitesimally small bar magnet of dipole moment \[\vec{M}\] is pointing and moving with the speed v in the \[\hat{x}\]- direction. A small closed circular conducting loop of radius a and negligible self- inductance lies in the y-z plane with its center at x = 0, and its axis coinciding with the x-axis. Find the force opposing the motion of the magnet, if the resistance of the loop is R. Assume that the distance x of the magnet from the center of the loop is much greater than a. |
| A. | \[\frac{21}{4}\frac{\mu _{0}^{2}{{M}^{2}}{{a}^{4}}v}{R{{x}^{8}}}\] |
| B. | \[\frac{16}{3}\frac{{{\mu }_{0}}{{M}^{2}}{{a}^{2}}{{v}^{2}}}{R{{x}^{3}}}\] |
| C. | \[\frac{3}{23}\frac{{{\mu }_{0}}Ma{{v}^{2}}}{R{{x}^{3}}}\] |
| D. | None of these |
| Answer» B. \[\frac{16}{3}\frac{{{\mu }_{0}}{{M}^{2}}{{a}^{2}}{{v}^{2}}}{R{{x}^{3}}}\] | |
| 2623. |
Two identical circular current carrying coils 1 and 2, each of radius R are placed adjacently a distance d apart (d |
| A. | \[\left| \left. {{L}_{1}} \right| \right.=\left| \left. {{M}_{21}} \right| \right.\] |
| B. | \[{{M}_{21}}>{{L}_{1}}\] |
| C. | \[{{L}_{1}}=-{{L}_{2}}\] |
| D. | \[{{M}_{12}}=-{{M}_{21}}\] |
| Answer» B. \[{{M}_{21}}>{{L}_{1}}\] | |
| 2624. |
The figure below depicts a circular loop of radius R carrying a fixed current I. The upper half of the loop is placed in a uniform magnetic field of magnitude B, perpendicular to the plane of the paper, as shown. The magnitude of the force on the loop is (neglect gravity) |
| A. | BIR |
| B. | 2BIR |
| C. | \[\pi BIR\] |
| D. | \[2\pi BIR\] |
| Answer» C. \[\pi BIR\] | |
| 2625. |
The two rails of a railway track, insulated from each other and the ground, are connected to a milli voltmeter. What is the reading of the milli voltmeter when a train travels at a speed of 180 km/hour along the track, given that the vertical component of earth's magnetic field is\[0.2\times {{10}^{-4}}\,weber/{{m}^{2}}\] and the rails are separated by 1 m? |
| A. | 1 |
| B. | 3 |
| C. | 5 |
| D. | 7 |
| Answer» B. 3 | |
| 2626. |
In a coil of resistance 100 Q, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is |
| A. | 250 Wb |
| B. | 275 Wb |
| C. | 200 Wb |
| D. | 225 Wb |
| Answer» B. 275 Wb | |
| 2627. |
A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with bigger loop is |
| A. | \[9.1\times {{10}^{-11}}\,weber\] |
| B. | \[6\times {{10}^{-11}}\,weber\] |
| C. | \[3.3\times {{10}^{-11}}\,weber\] |
| D. | \[6.6\times {{10}^{-9}}\,weber\] |
| Answer» B. \[6\times {{10}^{-11}}\,weber\] | |
| 2628. |
A metallic rod of length T is tied to a string of length U and made to rotate with angular speed co on a horizontal table with one end of the string fixed. If there is a vertical magnetic field 'B' in the region, the e.m.f. induced across the ends of the rod is |
| A. | \[\frac{2B\omega {{\ell }^{2}}}{2}\] |
| B. | \[\frac{3B\omega {{\ell }^{2}}}{2}\] |
| C. | \[\frac{4B\omega {{\ell }^{2}}}{2}\] |
| D. | \[\frac{5B\omega {{\ell }^{2}}}{2}\] |
| Answer» E. | |
| 2629. |
A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is |
| A. | 220 volt |
| B. | 440 volt |
| C. | 200 volt |
| D. | 400 volt |
| Answer» E. | |
| 2630. |
A rectangular coil of 200 turns of wire \[15\times 40\,c{{m}^{2}}\] makes 50 r.p.s. about an axis in its plane parallel to its longer side and perpendicular to a magnetic field of intensity \[0.08\,Wb/{{m}^{2}}\]. what is the instantaneous value of induced e.m.f. when the plane of the coil makes an angle with magnetic field of \[45{}^\circ \]. |
| A. | 213.3 V |
| B. | 301.7 V |
| C. | 151.5 V |
| D. | zero |
| Answer» B. 301.7 V | |
| 2631. |
A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it, the correct statement(s) is(are) I. The emf induced in the loop is zero if the current is constant. II. The emf induced in the loop is finite if the current is constant. III. The emf induced in the loop is zero if the current decreases at a steady rate. |
| A. | I only |
| B. | II only |
| C. | I and II |
| D. | I, II and III |
| Answer» B. II only | |
| 2632. |
When a metallic plate swings between the poles of a magnet |
| A. | no effect on the plate |
| B. | eddy currents are set up inside the plate and the direction of the current is along the motion of the plate |
| C. | eddy currents are set up inside the plate and the direction of the current opposes the motion of the plate |
| D. | eddy currents are set up inside the plate |
| Answer» D. eddy currents are set up inside the plate | |
| 2633. |
A simple electric motor has an armature resistance of \[1\Omega ~\] and runs from a dc source of 12 volt. When running unloaded it draws a current of 2 amp. When a certain load is connected, its speed becomes one-half of its unloaded value. What is the new value of current drawn? |
| A. | 7 A |
| B. | 3 A |
| C. | 5 A |
| D. | 0.166666666666667 |
| Answer» B. 3 A | |
| 2634. |
A motor having an armature of resistance \[2\Omega \]. Is designed to operate at 220 V mains. At full speed, it develops a back emf of 210V. When the motor is running at full speed, the current in the armature is: |
| A. | 3 A |
| B. | 5 A |
| C. | 7A |
| D. | 10A |
| Answer» C. 7A | |
| 2635. |
The back e.m.f. in a d.c. motor is maximum, when |
| A. | the motor has picked up max speed |
| B. | the motor has just started moving |
| C. | the speed of motor is still on the increase |
| D. | the motor has just been switched off |
| Answer» B. the motor has just started moving | |
| 2636. |
A circular coil is radius 5 cm has 500 turns of a wire. The approximate value of the coefficient of self-induction of the coil will be- |
| A. | \[25\text{ }mH\] |
| B. | \[25\times {{10}^{-3}}\,mH\] |
| C. | \[50\times {{10}^{-3}}\,mH\] |
| D. | \[50\times {{10}^{-3}}\,H\] |
| Answer» B. \[25\times {{10}^{-3}}\,mH\] | |
| 2637. |
A long solenoid has 500 turns. When a current of 2 ampere is passed through it, the resulting magnetic flux linked with each turn of the solenoid is \[4\times {{10}^{-3}}\,Wb\]. The self- inductance of the solenoid is |
| A. | 2.5 henry |
| B. | 2.0 henry |
| C. | 1.0 henry |
| D. | 40 henry |
| Answer» D. 40 henry | |
| 2638. |
A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating; It is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to: |
| A. | developement of air current when the plate is placed |
| B. | induction of electrical charge on the plate |
| C. | shielding of magnetic lines of force as aluminium is a paramagnetic material. |
| D. | electromagnetic induction in the aluminium plate giving rise to electromagnetic damping. |
| Answer» E. | |
| 2639. |
A conductor AB of length\[l\]moves in x - y plane with velocity \[\vec{v}={{v}_{0}}(\hat{i}-\hat{j})\]. A magnetic field \[\overset{\to }{\mathop{B}}\,={{B}_{0}}(\hat{i}+\hat{j})\] exists in the region. The iduced Emf is |
| A. | zero |
| B. | \[{{B}_{0}}l{{v}_{0}}\] |
| C. | \[{{B}_{0}}l{{v}_{0}}\] |
| D. | \[\sqrt{2}{{B}_{0}}1{{v}_{0}}\] |
| Answer» B. \[{{B}_{0}}l{{v}_{0}}\] | |
| 2640. |
A boat is moving due east in a region where the earth's magnetic field is \[5.0\times {{10}^{-5}}N{{A}^{-1}}\,{{m}^{-1}}\] due north and horizontal. The boat carries a vertical aerial 2 m long. If the speed of the boat is\[1.50\,m{{s}^{-1}}\], the magnitude of the induced emf in the wire of aerial is |
| A. | 0.75 mV |
| B. | 0.50 mV |
| C. | 0.15 mV |
| D. | 1 mV |
| Answer» D. 1 mV | |
| 2641. |
A rectangular loop has a sliding connector PQ of length \[\ell \] and resistance \[R\,\Omega \] and it is moving with a speed v as shown. The set-up is placed in a uniform magnetic field going m to the plane of the paper. The three currents \[{{I}_{1}},\,{{I}_{2}}\] and / are |
| A. | \[{{I}_{1}}=-{{I}_{2}}=\frac{Blv}{6R},\,I=\frac{2Blv}{6R}\] |
| B. | \[{{I}_{1}}={{I}_{2}}=\frac{Blv}{3R},\,I=\frac{2Blv}{3R}\] |
| C. | \[{{I}_{1}}={{I}_{2}}=I=\frac{Blv}{R}\] |
| D. | \[{{I}_{1}}={{I}_{2}}=\frac{Blv}{6R}\], \[I=\frac{Blv}{3R}\] |
| Answer» C. \[{{I}_{1}}={{I}_{2}}=I=\frac{Blv}{R}\] | |
| 2642. |
A wire of fixed lengths is wound on a solenoid of length \[\ell \] and radius r. Its self-inductance is found to be L. Now if same wire is wound on a solenoid of length \[\ell /2\] and radius r/2, then the self in- ductance will be - |
| A. | 2L |
| B. | L |
| C. | 4L |
| D. | 8L |
| Answer» B. L | |
| 2643. |
Two coils, one primary of 500 turns and one secondary of 25 turns, are wound on an iron ring of mean diameter 20 cm and cross-sectional area\[12\,c{{m}^{2}}\]. If the permeability of iron is 800, the mutual inductance is: |
| A. | 0.48 H |
| B. | 2.4 H |
| C. | 0.12 H |
| D. | 0.24 H |
| Answer» E. | |
| 2644. |
When the current in a certain inductor coil is 5.0 A and is increasing at the rate of 10.0 A/s, the potential difference across the coil is 140V. When the current is 5.0 A and decreasing at the rate of 10.0 A/s, the potential difference is 60V. The self-inductance of the coil is - |
| A. | 2H |
| B. | 4H |
| C. | 8H |
| D. | 12H |
| Answer» C. 8H | |
| 2645. |
A small square loop of wire of side \[\ell \] is placed inside a large square loop of wire of side \[L(L>\ell )\].The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to |
| A. | \[\ell /L\] |
| B. | \[{{\ell }^{2}}/L\] |
| C. | \[L/\ell \] |
| D. | \[{{L}^{2}}/\ell \] |
| Answer» C. \[L/\ell \] | |
| 2646. |
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be |
| A. | maximum in situation [a] |
| B. | maximum in situation [b] |
| C. | maximum in situation [c] |
| D. | the same in all situations |
| Answer» B. maximum in situation [b] | |
| 2647. |
A current of 1.5 A flows through a solenoid of length 20.0 cm, cross-section \[20.0\text{ }c{{m}^{2}}\] and 400 turns. The current is suddenly switched off in a short time of 1.0 millisecond. Ignoring the variation in the magnetic field the ends, the average back emf induced in the solenoid is: |
| A. | 0.3 V |
| B. | 9.6 V |
| C. | 30.0 V |
| D. | 3.0 V |
| Answer» B. 9.6 V | |
| 2648. |
Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction \[B={{B}_{0}}{{e}^{-t}}\]is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to. |
| A. | \[\frac{B_{0}^{2}\pi {{r}^{2}}}{R}\] |
| B. | \[\frac{{{B}_{0}}10{{r}^{3}}}{R}\] |
| C. | \[\frac{B_{0}^{2}{{\pi }^{2}}{{r}^{4}}R}{5}\] |
| D. | \[\frac{B_{0}^{2}{{\pi }^{2}}{{r}^{4}}}{R}\] |
| Answer» E. | |
| 2649. |
In an inductor of self-inductance L=2mH, current changes with time according to relation \[i={{t}^{2}}{{e}^{-t}}\]. At what time emf is zero? |
| A. | 4s |
| B. | 3s |
| C. | 2s |
| D. | Is |
| Answer» D. Is | |
| 2650. |
Figure shows a rectangular coil near a long wire. The mutual inductance of the combination is |
| A. | \[\frac{{{\mu }_{0}}a}{2\pi }ln\left( 1-\frac{b}{c} \right)\] |
| B. | \[\frac{{{\mu }_{0}}a}{2\pi }ln\left( 1+\frac{b}{c} \right)\] |
| C. | \[\frac{{{\mu }_{0}}a}{\pi }ln\left( 1+\frac{b}{c} \right)\] |
| D. | \[\frac{{{\mu }_{0}}a}{\sqrt{2}\pi }ln\left( 1+\frac{b}{c} \right)\] |
| Answer» C. \[\frac{{{\mu }_{0}}a}{\pi }ln\left( 1+\frac{b}{c} \right)\] | |