The correct choice is (a) 100.31 V
To explain: At resonance, | I | = (frac{V}{Z} = frac{V}{R} )
Given that, R = 40Ω and V = 100 V
∴ | I | = (frac{100}{40}) = 2.5 A
XL = ωL = 2π × 1000 × 0.5 × 10^-3
= 2π × 0.5 = 3.14 Ω
∴ VCOIL = I Z (At resonance)
= 2.5 (sqrt{40^2 + 3.14^2})
= 2.5 × 40.122 = 100.31 V.