Q18 (i) (a) A closed loop of area 1 m² and resistance of 10Ω is free to rotate about an axis passing through its plane and the centre. If the loop is placed at right angles to a magnetic field B = 0.2 Wb/m² and turned through 180° in 0.02 second, then determine (I) induced emf and (II) induced current in the loop.

(b) A wire is wound into a solenoid of length l and radius r. It has a self-inductance of L. By what factor does the self-inductance change, if the same wire is wound into a solenoid of half the length and half the radius?

OR

(ii) (a) In a series LCR circuit connected to an alternating voltage source of 220V50Hz, the readings of voltmeters across resistor, capacitor and inductor are 70V, 415V, 210V respectively.

If the value of the resistance R =100Ω, calculate

(1) current in the circuit.
(2) value of L.
(3) value of C.

(b) If the capacitance in an LC series circuit is doubled, by what value should the inductance be changed to keep its resonant frequency constant?

Solution

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