## anonymous one year ago You plug a string of 100 lights in series into a 120 V power outlet, and each light has a resistance of 3.00 Ω. If each light has a power rating of 0.50 W, what will happen? A. All the lights will go out. B. Only one light will go out. C. The string will remain lit. D. You cannot predict what will happen.

1. Michele_Laino

the total resistance is: 3*100=...ohms

2. anonymous

300!

3. Michele_Laino

ok! so the current is: I=120/300=...amperes

4. anonymous

0.4!

5. Michele_Laino

ok!

6. Michele_Laino

now the maximum current which can flow into each of the bulbs, is: I=W/R^2= 0.5/9=...amperes

7. anonymous

0.0555555...

8. anonymous

what does that mean? the lights will remain lit? :/

9. Michele_Laino

so, since 0.4>0.055, namely the current provided by the battery is greater than the maximum current which can flow into each bulb, wha can you conclude?

10. anonymous

ermm the string of lights will remain lit?

11. anonymous

choiceA?

12. Michele_Laino

sorry, I have made an error, the maximum current which can flow into each of the bulbs, is: $I = \sqrt {\frac{W}{R}} = \sqrt {\frac{{0.5}}{3}} = ...$

13. anonymous

0.408?

14. Michele_Laino

ok!

15. Michele_Laino

so, since 0.4<0.408, namely the current provided by the battery is less than the current which can flow into each bulb, what can you conclude?

16. anonymous

that means that all the lights will go out? choice A?

17. Michele_Laino

yes! that's right!

18. anonymous

yay!! thanks!!:D

19. Michele_Laino

:)