Passage VII

An RCL circuit contains an alternating current (AC) power supply, a resistor having a resistance R, a capacitor having a capacitance C, and an inductor having an induc­tance L (see Figure 1).

The capacitor and inductor each possess impedance, a type of electrical resistance. The angular frequency of the cur­rent, ω, is a measure of the number of times each second that the current reverses direction.

Figure 2 shows, for specific values of C, L, and average voltage, V, how the average current, I, varies with ω and with R.

Figure 2 adapted from David Halliday and Robert Resnick, Physics, Part 2, 3rd ed. ©1978 by John Wiley and Sons, Inc.

For a given R, the peak average current, Imax, occurs at the resonant angular frequency, ω0 .

Figure 3 shows how ω0 varies with L and C.

38. For the conditions specified in Figure 2 and R = 30 ohms, the resistor will generate the greatest amount of heat when ω is closest to which of the fol­lowing values?

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

When the resistance Impedance is the largest, the more heat is generated. Look at the line segment corresponding to R=30 ohms in figure 2. When the abscissa is 1.0, the ordinate I reaches the maximum value