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If a “75-W” bulb (see 25.35) is connected across a 220-V
Chapter 25, Problem 40E(choose chapter or problem)
Problem 40E
If a “75-W” bulb (see Problem 25.35) is connected across a 220-V potential difference (as is used in Europe), how much power does it dissipate? Ignore the temperature dependence of the bulb’s resistance.
25.35 . Light Bulbs. The power rating of a light bulb (such as a 100-W bulb) is the power it dissipates when connected across a 120-V potential difference. What is the resistance of (a) a 100-W bulb and (b) a 60-W bulb? (c) How much current does each bulb draw in normal use?
Questions & Answers
QUESTION:
Problem 40E
If a “75-W” bulb (see Problem 25.35) is connected across a 220-V potential difference (as is used in Europe), how much power does it dissipate? Ignore the temperature dependence of the bulb’s resistance.
25.35 . Light Bulbs. The power rating of a light bulb (such as a 100-W bulb) is the power it dissipates when connected across a 120-V potential difference. What is the resistance of (a) a 100-W bulb and (b) a 60-W bulb? (c) How much current does each bulb draw in normal use?
ANSWER:
Solution 40E
Step 1
Calculate the resistance.
Here, is resistance, is voltage and is power.
Substitute for and for .