Physics Multiple Choice on Power and Resistance [PLEASE HELP] Watch

uberteknik
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#21
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(Original post by nwmyname)
uberteknik Abeh here, in this question, why is x positive but not negative?
Internationally standardised (ISO) circuit symbol for the battery using the conventional current definition:

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uberteknik
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(Original post by voltz)
So essentially we are just finding the ratio of voltage in the resistors and using that? I managed t get the ration of 2/3 by assigning the same resistance to each and finding the total resistance. Then, worked out ratio of P and multiplied by 12 to get 8
Yup. That's all you need.
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nwmyname
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#23
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(Original post by uberteknik)
Internationally standardised (ISO) circuit symbol for the battery using the conventional current definition:

can you explain how this is? I thought nve to pve?

How is this wrong?
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voltz
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(Original post by nwmyname)
can you explain how this is? I thought nve to pve?

How is this wrong?
Coventional current goes from positive to negative whereas the elecric current goes from negative to positive

I dont know if that answers your question
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uberteknik
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(Original post by nwmyname)
can you explain how this is? I thought nve to pve?

How is this wrong?
As voltz said, in a conductor, electron actual flow is from -ve to +ve.

Historically, when electricity was discovered, no-one knew about atoms let alone electrons and charge carriers. Benjamin Franklin (in the 19th century) decided an arbitrary convention where he thought charge flowed from +ve to -ve (smooth wax to rough wool in his experiments).. As sods luck would have it, he chose incorrectly when the true nature of electricity in conductors was identified in the first part of the 20th century.

By that time, Franklins convention was in such widespread use, it was deemed too difficult and unnecessary to change, so it stuck and we still use it to this very day - otherwise known as 'conventional current'.

In reality, as long as everyone uses the same convention (which we do), then it does not make any difference to calculations or outcomes whatsoever.

This is also one of the reasons why the Anode and Cathode terminology is used, to remove ambiguity when describing the physical nature of electron flow.
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