- #1

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So my attempt has been this but I'm not exactly sure whether or not so just making sure this would be the answer.

[117/(179+r)]^2(179)=76

sqrt(76/179)=0.652 A

(0.652 x 179)= 116.708

117-116.708=0.364

0.364/0.652=0.558 ohm

- Thread starter Lizziecupcake
- Start date

- #1

- 5

- 0

So my attempt has been this but I'm not exactly sure whether or not so just making sure this would be the answer.

[117/(179+r)]^2(179)=76

sqrt(76/179)=0.652 A

(0.652 x 179)= 116.708

117-116.708=0.364

0.364/0.652=0.558 ohm

- #2

- 1,506

- 17

I got the same answer as you to 2 significant figures

- #3

- 5

- 0

So this would be the correct method to solve this question?I got the same answer as you to 2 significant figures

- #4

- 1,506

- 17

I prefer to break the question down into separate parts rather than produce 1 equation. What I did was:

76W, 179Ω so V^2/179 = 76

which gives V = 116.64 volts across the lamp, this means 117-116.64 volts = 0.36Vacross the internal resistance.

Also I^2.R =76W so this gives I = 0.652A flowing from the battery

So internal resistance = V/I = 0.36/0.652 = 0.552Ω

This is why I quoted my answer to 2 sig figs, I used V = 0.36 rather than the 0.364 that you used.

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