Chapter 19, Problem 15P

To determine

The resistance of each bulb.

Answer to Problem 15P

The resistance of each bulb is $26.91\Omega$ .

Explanation of Solution

Given info:

Voltage of the source, $V=110\text{V}$

Power of each bulb, $P=7\text{W}$

Number of Christmas tree lights, $n=8$

Formula Used:

The expression to calculate the current through each bulb is,

  $I=\frac{nP}{V}$

The expression to calculate the resistance of each bulb is,

  $R=\frac{P}{I^2}$

Calculation:

Substitute al the values in the above expression.

  $\begin{array}{c}I=\frac{8\left(7\text{W}\right)}{110\text{V}}\\ =0.51\text{A}\end{array}$

Substitute al the values in the above expression.

  $\begin{array}{c}R=\frac{7\text{W}}{{\left(0.51\text{A}\right)}^2}\\ =26.91\Omega \end{array}$

Conclusion:

Therefore, the resistance of each bulb is $26.91\Omega$ .