Question

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

Answer 1

Correct Answer - C
`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`