AL phy MC Q 32--LR circuit

current (rms) through the circuit I = Vo/Z
where Vo is the rms voltage of the ac source,
Z is the impedance of the circuit

But Z = square-root[(wL)^2 + R^2]
hence, I = Vo/square-root[(wL)^2 + R^2]

Voltage (rms) across the resistor Vr = I.R = R.(Vo)/square-root[(wL)^2 + R^2]
Statement (1): inserting an iron core increases the value of inductance L of the inductor. Hence Vr decreases.
Statement (2): increase the frequency w of the ac supply will decrease the value of Vr.