When `1A` is passed through three coils `A,B,C` in series the voltage drops are respectively 6,3 and 8 volt on direct current source and 7,5 and 10 volt on Alternating current source
Power factor of whole circuit when atlernating current flow

Options

A. 0.6
B. 0.8
C. 0.78
D. 1

Answer

C

Explanation

`R_(A) = 6, R_(B ) = 3, R_(C ) = 8`
`Z_(A) = 7, Z_(B) = 5, Z_(C ) = 10`
`R` (total) `= 6 + 3 + 8 = 17 Omega`
`X_(A) = sqrt(7^(2) - 6^(2)) = 3.6 Omega`
`X_(B) = 4 Omega , X_(C ) = 6 Omega`
X (total) `= 3.6 + 4 + 6 = 13.6 Omega`
Total impedance `= sqrt(R^(2) + X^(2)) = 21.8 m`
Power factor `= (R )/(Z) = (17)/(21.8) = 0.78`