Electromagnetic Induction

Problem 169: A magnetic coil produces 100,000 maxwells with 2,000 turns and with a current of 2 A. The current is cut-off and the flux collapses in 0.01 sec. What is the average voltage that will appear across the coil?

Problem 170: A magnet, which generates 800 maxwells of flux, is inserted through a coil of 1000 turns. It is then withdrawn within 0.15 sec. What is the voltage that appears across the coil?

Problem 171: The armature coil of a generator with 50 conductors on it rotates in a magnetic field with a magnetic flux density 1.5 T. The effective area of the coil is 1000 square cm. If this coil is move across the pole in 0.5 sec, determine the average emf induced in the coil.

Problem 172: A conductor, 50 mm long, moves at a velocity of 2.5 meters per second across a magnetic field of \(0.90\,Wb/m^2\). What is the voltage generated?

Problem 173: An airplane travels at a speed of 1000 kph in a region where the earth's magnetic field is \(5.0\times10^{-5}\,T\) and is nearly vertical. What is the potential difference induced between the wing tips of the airplane, which is 20 m apart?

Problem 174: A piece of conductor 10 cm long moves across a magnetic field of 10,000 gauss at a velocity of 120 cm/sec. What voltage appears across the conductor?

Problem 175: A conductor 50 cm in length moves at an angle of 30° to the direction of a magnetic field with a velocity of 100 cm/s. If the field has a flux density of \(2\,Wb/m^2\), calculate the emf induced in it.

Problem 176: A metal disk of 30 cm radius rotates at an angular velocity of 1200 rpm across a uniform vertical magnetic field of flux density \(0.5\,Wb/m^2\). Calculate the voltage induced between the rim and the center of the disk.

Problem 177: A conducting disc 20-cm in diameter pivoted by a vertical spindle which is lying in uniform vertical magnetic field of flux density 0.3 T. A fixed brush is connected at the edge of the disc. When a 4 ohm resistance is connected across the brush and the spindle, a current of 15 mA was observed to flow through the resistor. Determine the velocity in which the disc is rotating.

Problem 178: How much is the inductance of a coil that induces 500 V when the current changes at the rate of 5 mA in 2 \(\mu s\)?

Problem 179: The field winding of a DC generator is wound with 900 turns and has a resistance of 50 ohms. If the winding is excited from a 240 V dc source, the magnetic flux linking the coil is 4 mWb. Determine the self-inductance of the coil.

Problem 180: A coil of 1000 turns is uniformly wound on a ring of non-magnetic material, the mean diameter being 20 cm. The cross sectional area of the coil is 4 square cm. Determine the self-inductance of the coil.

Problem 181: An iron core 0.4 m long and 5 square cm. in cross section, is wound with 300 turns. When a current of 0.5 A flows in the coil, how much is the inductance of the coil. Assume the core has a permeability of 2500.

Problem 182: What is the coefficient of coupling of two coils whose mutual inductance is 1 H and whose self-inductance are 1.2 and 2 H?

Problem 183: A coil of inductance 8 mH, produces \(80\,\mu Wb\) of magnetic flux. Of this total flux, \(60\,\mu Wb\) are linked to a second coil of inductance 2 mH, how much is the mutual inductance between coils?

Problem 184: The total inductance of two coils, A and B when connected in series aiding is 0.5 H and 0.2 H when connected in series opposing. Coil A when isolated from coil B has a self-inductance of 0.2 H. Calculate the self-inductance of coil B.

Problem 185: Two identical coils with self-inductance of \(250\,\mu H\) each are connected in series. When connected series aiding, the equivalent inductance is \(550\,\mu H\) and \(450\,\mu H\) when connected series opposing. How much is the coupling coefficient of two coils?

Problem 186: A cylinder whose radius is 2 cm and altitude of 100 cm. is uniformly wound with 2500 turns of wires in a single layer. A second layer of 100 turns and of much finer wires is wound over the first near its center. Calculate the mutual inductance of the two coils.

Problem 187: Two coils having 200 and 300 turns respectively are wound side by side on a common closed core whose cross section is \(100\,cm^2\) and mean length of 200 cm. What will be the voltage induced in the second coil if the current in the first coil changes from 0 to 5 A in 0.05 second. Assume relative permittivity of the core to be 1500.

Problem 188: The energy (Wo) stored in a coil is dependent in the inductance (L) of the coil and the current flowing. If the inductance were doubled with the same current flowing, what would be the resulting stored energy?