Calculating potential difference

[sallyishyper]

I have done 1, i can't get the right answer for question 2. i seem to be getting minus7.5 volts. i know that's not anywhere near right because you can't get a minus voltage. i have tried many different ways to do this and i still can't get the right answer

To get question 1 i used ohms law which gave me the two answers shown in the attachment, for question 2 i tried using the same method, but that gave me the wrong answer so i tried finding the conductance and from the resistance and the current, but that gave me - 7.5 volts. i ma very confused an i think i might be missing something very simple

https://www.physicsforums.com/attachments/16093

 

[alphysicist]

Hi sallyishyper,

I have done 1, i can't get the right answer for question 2. i seem to be getting minus7.5 volts. i know that's not anywhere near right because you can't get a minus voltage. i have tried many different ways to do this and i still can't get the right answer

To get question 1 i used ohms law which gave me the two answers shown in the attachment, for question 2 i tried using the same method, but that gave me the wrong answer so i tried finding the conductance and from the resistance and the current, but that gave me - 7.5 volts. i ma very confused an i think i might be missing something very simple

https://www.physicsforums.com/attachments/16093

Your attachment does not seem to be there.

 

[tmusgrove]

I couldn't get the attachment either, says that there is an error.

 

[tiny-tim]

Hi sallyishyper!

Can you give us the url of your picture?