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A typical light dimmer used to dim the stage lights in a
Chapter , Problem 56(choose chapter or problem)
A typical light dimmer used to dim the stage lights in a theater consists of a variable inductor L (whose inductance is adjustable between zero and Lmax) connected in series with a lightbulb B, as shown in Fig. 31-34. The electrical supply is 120 V (rms) at 60.0 Hz; the lightbulb is rated at 120 V, 1000 W. (a) What Lmax is required if the rate of energy dissipation in the lightbulb is to be varied by a factor of 5 from its upper limit of 1000 W? Assume that the resistance of the lightbulb is independent of its temperature. (b) Could one use a variable resistor (adjustable between zero and Rmax) instead of an inductor? (c) If so, what Rmax is required? (d) Why isnt this done?
Questions & Answers
QUESTION:
A typical light dimmer used to dim the stage lights in a theater consists of a variable inductor L (whose inductance is adjustable between zero and Lmax) connected in series with a lightbulb B, as shown in Fig. 31-34. The electrical supply is 120 V (rms) at 60.0 Hz; the lightbulb is rated at 120 V, 1000 W. (a) What Lmax is required if the rate of energy dissipation in the lightbulb is to be varied by a factor of 5 from its upper limit of 1000 W? Assume that the resistance of the lightbulb is independent of its temperature. (b) Could one use a variable resistor (adjustable between zero and Rmax) instead of an inductor? (c) If so, what Rmax is required? (d) Why isnt this done?
ANSWER:Problem 56
A typical light dimmer used to dim the stage lights in a theatre consists of a variable inductor L (whose inductance is adjustable between zero and 
(a) What
(b) Could one use a variable resistor (adjustable between zero and 
(c) If so, what
(d) Why isn’t this done?
Step by Step Solution
Step 1 of 4
Given data:
The power P is 1000 W
The voltage supply V is 120 V
The frequency f is 60 Hz
(a)
The average power is:
Since the average power directly varies with square of current:
