Question

Eight 7.0-W Christmas tree lights are connected in series to each other and to a 110-V source. (a) Show the illustration (b) What is the resistance of each bulb?

Answer 1

Part (a)

(B)

Total power

$P=7\times8=56W$

Now current

$I=\frac{56}{110}=0.509A$

$R_1=\frac{P}{I^2}=\frac{7}{0.509^2}=27.01\Omega$

Similarly

$R_2=\frac{P}{I^2}=\frac{7}{0.509^2}=27.01\Omega$

$$R_3=R_4=R_5=R_6=R_7=R_8=27.01\Omega$$