Two coils having equal resistance but different inductances

Two coils having equal resistance but different inductances are connected in series. The time constant of the series combination is—

1. Sum of the time constants of the individual coils.
2. average of the time constants of individual coils.
3. geometric mean of the time constants of individual coils.
4. product of the time constants of the individual coils.

According to the given question.

Above two coils are in the series.
The equivalent impedance = (R₁ + R₂) + J (L₁ + L₂)

Time constant _eq =		L₁	=	L₁ + L₂
		R_eq		R₁ + R₂

Given that R₁ = R₂ then _eq =	L₁ + L₂
	2R

i =		L₁	; ₂ =	L₂
		R₁		R₂

₁ + ₂ =		L₁	+	L₂	=	L₁+ L₂	= 2 _eq
		R₁		R₂		R

or _eg =	₁ + ₂
	2