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.
A394 rpm
B382 rpm
C302 rpm
D228 rpm
#2📜 EE Board April 1992📘 1001 RojasHard
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.
A0.16 H
B0.12 H
C0.20 H
D0.15 H
#3📘 1001 RojasHard
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.
A52.3 V
B67.8 V
C62.6 V
D58.6 V
#4📘 1001 RojasHard
Problem 190: Two coils having self-inductance and mutual inductance of 3H, 2H and 1H respectively are connected in series. If a current of 4 A is passed through the coil, evaluate the ratio of the energy stored in the magnetic field when the fluxes (self and mutual) are in the same direction to the energy stored when the said fluxes are against each other.
A3.24
B2.33
C1.73
D2.67
#5📜 EE Board April 1995📘 1001 RojasHard
Problem 191: Two coils of inductances 4 and 6 henry are connected in parallel. If their mutual inductance is 3 henry, calculate the equivalent inductance of the combination if mutual inductance assist and if mutual inductance opposes the self-inductance respectively.
A2.4 H & 1.4 H
B3.75 H & 0.94 H
C6.25 H & 2.75 H
D16 H & 4 H
#6📘 1001 RojasHard
Problem 192: A 50-mH inductor is charged to store 1 J of energy. If an uncharged 30-mH inductor is then connected across its terminals, how much energy is transferred to the second inductor?
A0.154 J
B0.262 J
C0.234 J
D0.141 J
#7📜 EE Pre-Board March 2014📘 PowerhouseHard
When one coil of a magnetically coupled pair has a current of 5 A, the resulting fluxes \(\phi_{11}\) and \(\phi_{12}\) are 0.4 and 0.8 mWb, respectively. If the turns are \(N_1\) = 500 and \(N_2\) = 1,500, find \(L_2\).
