a. The inductance of an air-core coil is 0.08 H, and the effective resistance is 4Ω when a 60-V, 50-Hz source is connected across the coil. Find the current passing through the coil and the reading of a wattmeter across the coil.
b. If a brass core is inserted in the coil, the effective resistance increases to 7Ω , and the wattmeter reads 30 W. Find the current passing through the coil and the inductance of the coil.
c. If a solid iron core is inserted in the coil, the effective resistance of the coil increases to 10Ω , and the current decreases to 1.7
Find the wattmeter reading and the inductance of the coil.