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Two (insulated) coils are wound, (one over the other), on a solenoid core. If the number of turns, per unit length, of the first coil and of the second coil, were to be increased by a factors of 3 and 4, respectively, the self inductance of the two coils (L1 and L2) and their mutual inductance (M), would increase (respectively) by factors of (1) 3, 4 and 12 (2) 3, 4 and 4/3 (3) 9, 16 and 16/9 (4) 9, 16 and 12

asked
Jan 13
by
anonymous

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**Description :** A (long thin) solenoid core has an insulated primary coil, (of n1 turns per unit length) and an insulated secondary coil, (of n2 turns per unit length) wound on top of the primary coil. The cross sectional area of the solenoid, equals ... M = \((\frac{L^2_1}{L^2_2})\) (4) M = \((\frac{L^2_2}{L_1})\)

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**Description :** A (solenoid) coil is wound on a core of square cross-section. If all the linear dimensions of core are increased 2 times, but the number of turns per unit length of the coil, remains same, the self inductance would increases by a factor of (1) 2 (2) 4 (3) 8 (4) 16

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**Description :** Two coils m and n having 10 turns and 15 turns respectively are placed close to each other. When 2A current is passing through coil m, then flux linked with coil n is 1.8 x 10-4 wb per turn. If 3A current passed through coil n, then calculate the flux linked per turn of coil m.

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**Description :** An air cored coil has a self inductance of 0.1 H. A soft iron core of relative permability 1000 is introduced and the number of turns is reduced to 1/10th of the previous value. Find the new value of self inductance.

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**Description :** Two circular loops, of radii R and r (R >> r), respectively, are positioned, parallel to each other, in the yz plane. The centres and axis, of both the loops, lie on the x-axis, a distance x apart. The larger loop has N turns, ... {μ_0\pi}{2x^2}(nN)(Rr^2)\) (4) \(\frac{μ_0\pi}{2x^3}(nr^2)(NR^2)\)

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**Description :** A pair of (insulated) coils having of n1 and n2 tunrs, are kept close together. When the current, passing through the first, is reduced at a rate r, an emf of 3mV is developed across the other coil. If the second coil were to ... across the first coil will be (1) 1.5 mV (2) 2.0 mV (3) 3 mV (4) 6 mV

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**Description :** In a Hartley oscillator, L1 = 0.1 mH, L2 = 10 µH and mutual inductance between coils equals 20 µH. The voltage gain needed for sustained oscillations should be (a) 2.37 (b) 0.1 (c) 11.54 (d) 9.09

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**Description :** A conducting coil of 600 turns has a self inductance of 108 mH. The self inductance of a second identical coil, having of 500 turns, will be (1) 75 mH (2) 90 mH (3) 130 mH (4) 155 mH

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**Description :** A long solenoid of radius 0.01 m has 600 turns per meter. A smaller coil of 100 turns is wrapped closely around the centre of the bigger solenoid. If the current in the solenoid rises from zero to 2A in 1ms. Find the emf induced in smaller coil.

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**Description :** Consider two coplanar, co-centric circular coils having radius r1 and r2 (r2 > r1) as shown in the figure. The mutual inductance between these two coils will be (1) \(\frac{μ_0\pi r^2_1}{2r_2}\) (2) \(\frac{μ_0\pi r_1}{2r_2}\) (3) \(\frac{μ_0\pi r^2_2}{2r_2}\) (4) \(\frac{μ_0\pi r^2_1}{2r_1}\)

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**Description :** The coefficient of mutual inductance of two circuits A and B is 3 mH and their respective resistances are 100 hm and 4 ohm. How much should the currents change, in 0.02 second, in circuit A, so that an induced current 0.006 ampere flows ... the circuit B? (1) 0.16 A (2) 0.18 A (3) 0.24 A (4) 1.6 A

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**Description :** A mini generator has a coil of 1000 turns, each of area 10-2m2 . The coil is placed with its plane perpendicular to a uniform magnetic field of intensity 25 mT and is rotated at a uniform rate of 100 rotations per ... 3) 100 volt, 0 volt, 100 volt, 0 volt (4) 100 volt, 100 volt, 100 volt, 100 volt

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**Description :** A spring, of spring constant 100 N/M, is compressed through a distance of 4cm. The potential energy, stored in this compressed spring, equals the work done, by the source', in establishing a current of 2A in a given ... self inductance of the coil equals (1) 20 mH (2) 40 mH (3) 60 mH (4) 80 mH

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**Description :** The self-inductance of a long solenoid with a turns per unit length is: a. L = μ nA/ l b. L = μ n2 A/ l c. L = μ n2 A l d. L = μ n l/ A

**Last Answer :** d. L = μ n l/ A

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**Description :** A rectangular coil, of 300 turns, has an average area of 25 cm x 10 cm. The coil rotates, with a speed of 50 cycles per second, in a uniform magnetic field of 4 x 10-2T, about an axis perpendicular to the field. The peak value of induced emf (in volt), is (1) 3 π (2) 30 π (3) 300 π (4) 3000 π

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**Description :** The current ‘i’ in a coil of self inductance 'l' varies with time as shown in figure. The variation of the induced emf 'ε' with time would than be represented by the graph labelled as graph (1) A (2) B (3) C (4) D

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**Description :** The current, through a coil of self inductance. L = 2mH, is given by I = t2 e-t at time t. The time taken, to make the induced emf zero, will be (1) 1 S (2) 2 S (3) 3 S (4) 4 S

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**Description :** The inductance of a long solenoid of length 1000 mm wound uniformly with 3000 turns on a cylindrical paper tube of 60 mm diameter is (A) 3.2 µH (B) 3.2 mH (C) 32.0 mH (D) 3.2 H

**Last Answer :** The inductance of a long solenoid of length 1000 mm wound uniformly with 3000 turns on a cylindrical paper tube of 60 mm diameter is 32.0 mH

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**Description :** A 50 turns circular coil has as average a radius of 3 cm. It is kept in a magnetic field acting normal to the area of the coil. The magnetic field B is increased from (0.10 T) to (0.35 T) in 2 ms. The average induced emf in the coil, would be (1) 0.177 V (2) 1.77 V (3) 17.7 V (4) 177 V

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**Description :** A circular coil, of radius a, (having N turns) is made to rotate about its vertical diameter with an angular speed ω. The coil is present in a region where a uniform horizontal magnetic field B is present. If the coil has a resistance ... a^2 ωB}{\sqrt{2}R}\) and \(\frac{(N\pi a^2 ωB)}{\sqrt{2}R}\)

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**Description :** A small square loop of wire, of side l, is placed inside a large square loop of wire of side L (L >> l). The loops are coplanar and their centres coincide. The mutual inductance of the system is proportional to (1) \(\frac{l}{L}\) (2) \(\frac{l^2}{L}\) (3) \(\frac{l}{L}\) (4) \(\frac{L^2}{l}\)

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**Description :** A small circular loop, of radius 3cm, and a bigger loop, of radius 20cm, are placed coaxially, at a distance of 15cm as shown in the figure. A current of 2A flows through the smaller loop. Find the flux linked with the bigger loop and the mutual inductance of the two loops.

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**Description :** If both the number of turns and core length of an inductive coil are doubled, then its self inductance will be (a) halved (b) doubled (c) quadrupled (d) unaffected

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**Description :** A coil of area 500 cm2 and 2000 turns is kept normal to a magnetic field of 4 x 10-5 Wb/m2 . It is rotated through 1800 in 0.1 second. (i) Calculate the average induced emf (ii) if the total resistance of circuit be 20 ohm, calculate the induced charge.

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**Description :** A small coil, having n turns each of (everage) radius r, is held normal to the magnetic field liens in the region between the (flat) pole pieces of a horse shoe magnet. The terminals ofthe coil are connected to a ... the magnetic field), is the graph labelled as graph. (1) K (2) L (3) M (4) N

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**Description :** Two students, working in the same laboratory, do the experiment on finding the velocity of sound using the resonance tube column apparatus'. They used tubes of diameters D1 and D2 and identical tuning forks of frequency N each. The first and ... 1= l1 + 0.3 (D1 - D2)]; [l'2 = l2 + 0.9 (D1 - D2)]

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**Description :** A current of 4A flows in a coil when connected to 12V dV source. If the same coil is connected to a 12V, 50 rad/s a.c. source, a current of 2.4 A flows in the circuit. Determine the ... the coil. Also find the power developed in the circuit if a 2500μF capacitor is connected in series with the coil.

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**Description :** The experiment, using a resonance tube set-up, was carried out in a room at a temperature θ°C . The tuning fork used had a frequency N(Hz) and the first and second positions of resonance were observed for lengths l1 (cm) and l2 (cm ... (4) \(\frac{N(l_2+l_1)}{50}(1+\frac{\theta}{273})^{-1/2} (m/s)\)

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**Description :** Consider a source computer(S) transmitting a file of size 106 bits to a destination computer (D)over a network of two routers (R1 and R2) and three links(L1, L2, and L3). L1connects S to R1; L2 connects R1 to ... file from S to D? a. 1005 ms b. 1010 ms c. 3000 ms d. 3003 ms Answer: Option(a)

**Last Answer :** a. 1005 ms

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**Description :** When the current in a coil changes from +2A to –2A in 0.05 second, an emf of 8V is induced in a coil. The coefficient of self induction of the coil is (1) 0.1 H (2) 0.2 H (3) 0.4 H (4) 0.8 H

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**Description :** A planar circular coil, of radius a, has N turns and it can be made to rotate about its diameter as axis. The coil has a resistance R and is present in a region where a uniform magnetic field, B ... spin' at start, it would then keep on rotating at its initial rate, due to its rotational inertia'.

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**Description :** A student sets up the speed of sound in air apparatus for finding the velocity of sound in air, at the room temperature. Using a tuning fork, of frequency n (Hz), she obtains the first and second positions of resonance for lengths l1 (m) and ... (2) V = 4/3 l2n (3) V = 2(l2 - l1)n (4) V = (l2 + l1)n

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**Description :** Two coils have a mutual inductance 0.005H. The current changes in the first coil according to the equation `I=I_(0) sin omegat "where" I_(0)=10A and o

**Last Answer :** Two coils have a mutual inductance 0.005H. The current changes in the first coil according to the equation `I ... (pi//x)` volts. Find the value of x.

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**Description :** The inductance, capacitance and resistance in a given series LCR circuit, have values of (n) henry, (1/n3) farad and (n2) ohm. The quality factor, Q, and the resonant frequency (v0) , of this circuit, equal, respectively, (1) \(Q=\ ... frac{2\pi}{n}\) (4) \(Q=\frac{8\pi^2}{n^2}; v_0=\frac{4\pi}{n}\)

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**Description :** An electrical circuit is made up of an inductance (L), a capacitor (C) and a resistor (R), connected in series. When it is connected across the mains (Voltage = 111.8 V ≃ 12500 V), it draws 125W power from these mains. ... , 142Ω (2) 106.5Ω , 213Ω , 106.5Ω (3) 89Ω , 178Ω , 89Ω (4) 71Ω , 142Ω , 71Ω

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**Description :** A given series LCR circuits is connected across a simusoidal AC voltage source. v = v0 sin (ωt) The inductance, L, in the circuit, has a value equal to 1/ω2C. The rms voltage drop, across L, C, and R, of this circuit, are ... {2}}\) (4) \(\frac{v_0}{\sqrt{2}R}.\frac{1}{ωC};\frac{v_0}{R}\) and v1

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**Description :** When an operating motor is connected to the controller shown in the illustration, the a path of current flow through the circuit is ____________. EL-0010 A. 'L1', stop button, start button, coil 'CR', 'L2' B. 'L1' ... L2' D. 'L1', stop button, start button, 'CR' contact, 'M' contact, 'CR' coil, 'L2'

**Last Answer :** Answer: B

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**Description :** If two coils are wound on a single iron core, what will a change in current in one coil cause in the other coil?

**Last Answer :** A change in inductance.

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**Description :** The differential coupling of two coils in series connection has self-inductance of 2 mH & 4 mH & a mutual inductance of 0.15 mH. The equivalent inductance of the combination is: (A) 5.7 mH (B) 5.85 mH (C) 6 mH (D) 6.15 mH

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**Description :** When number of turns in a coil is trippled, without any change in the length of coil, its self inductance becomes? (1) Nine times (2) Three times (3) Six times (4) One-third

**Last Answer :** (1) Nine times

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**Description :** When number of turns in a coil is trippled, without any change in the length of coil, its self inductance becomes? (1) Nine times (2) Three times (3) Six times (4) One–third

**Last Answer :** Nine times

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**Description :** An iron rod 0.2m long, 10 mm in diameter and of permeability 103 , is placed inside a long solenoid wound with 300 turns/meter. If a current of 0.5A is passed through the rod, total magnetic moment of the rod would be (nearly) (1) 2335 SI Unit (2) 233.5 SI Unit (3) 23.35 SI Unit (4) 2.335 SI Unit

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**Description :** A solenoid has 400 turns, of wire wound on a cylinder of radius 5 cm and length 40 cm. Calculate the magnetic field at the (a) midpoint of the solenoid and (b) a point, on the axis, 2cm from one end, of the solenoid, when a current of 1A flows through it.

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**Description :** The magnetic flux, through a coil, present in a magnetic field, directed perpendicular to its plane, varies with time (in second) according to the relation. ϕB = 6t2 + 7t + 1 (ϕB in miliweber) Find the ... at t = 2s. Also find the current, and its direction, in the resistance R, if R = 10Ω

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**Description :** If l1 and l2 are the lengths of long and short spans of a two way slab simply supported on four edges and carrying a load w per unit area, the ratio of the loads split into w1 and w2acting on strips parallel to l2 and l1 is (A) ... l1 (B) w1/w2 = (l2/l1)² (C) w1/w2 = (l2/l1)3 (D) w1/w2 = (l2/l1)

**Last Answer :** Answer: Option D

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**Description :** A coil of 500 turns is linked with a flux of 25 mwb, when carries a current of 12.5A. Calculate the value of self-inductance.

**Last Answer :** Ans: Self-Inductance: L = NΦ /I = 500 × 25 × 10-3 / 12.5 = 1 H

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**Description :** The diagram, given here, shows a step-up' that may be used to supply power from a power plant' to a town' via transmission lines of a total (to and fro) length of 50 kM. The power requirement, of the town is 2 ... , used at the power plant, should be (1) 4400 V (2) 16900 V (3) 20600 V (4) 29400 V

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**Description :** Calculate the mutual inductance of two tightly coupled coils with inductances 49H and 9H. a) 21 b) 58 c) 40 d) 49/9

**Last Answer :** a) 21

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