Correct Option: B

KCL at node A

	VA – 10 cos 2t	+	VA – 0		=	3	Vi ...................(i)
	4		1 +	1		4
				sC

Again from given circuit –

	V1	=	VA – 10 cos 2t	................(ii)
	4		4

or V_i = 10 cos2t – V_A ...................(iii)
From equations (i) and (iii)

	VA – 10 cos 2t	+ VA		sC		=	3	(10 cos 2t – VA)
	4			1 + sC			4

or VA	1	+	j	+	3
	4		3 + j		4

= 10 cos 2t		3	+	1
		4		4

or VA		1 +	j2		= 10 cos 2t
			3 + j2

VA = 10 cos 2t		3 + 2j
		3 + 4j

Current supplied by voltage source, say

I =	10 cos 2t – VA
	4

or I =	1		10 cos 2t – 10 cos 2t	(3 + 2j)
	4			3 + 4j

or I =	10	cos 2t		3 + 4j – 3 – 2j
	4			3 + 4j

or I = 2.5 cos 2t			2j
			3 + 4j

or I = 2.5 cos 2t	2		90°
	5		53.13°

or I = cos 2t 36.86º
Since here current leads voltage, hence power factor will be leading and
cos φ = cos 36.86º = 0.8
Hence alternative (B) is the correct choice.