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Metro_Mystery
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I'm having a lot of difficulty understanding a really simple concept in my first year physics text. See the diagram below...
http://www.avhq.com.au/~metrosexuality/ele_pass_conv.JPG
"First, consider Figure 1.5-1a. When the current enters the circuit element at the + terminal of the voltage and exits at the −terminal, the voltage and current are said to “adhere to the passive convention.” In the passive convention, the voltage pushes a positive charge in the direction indicated by the current. Accordingly, the power calculated by multiplying the element voltage by the element current p = vi is the power absorbed by the element. (This power is also called “the power received by the element” and “the power dissipated by the element.”)"
I have read over that paragraph hundreds of times; and still don't understand it... If a positive charge is entering the + terminal of a voltage element, wouldn't the voltage be pushing the charge against the flow of current?
Likewise-
Next, consider Figure 1.5-1b. Here the passive convention has not been used. Instead, the current enters the circuit element at the −terminal of the voltage and exits at the +terminal. In this case, the voltage pushes a positive charge in the direction opposite to the direction indicated by the current. Accordingly, when the element voltage and current do not adhere to the passive convention, the power calculated by multiplying the element voltage by the element current is the power supplied by the element.
If a positive charge is entering the - of a voltage element, wouldn't work need to be done IN the direction indicated by the current to keep the current flowing?
It just doesn't make sense...
Can someone please help clarify this? It's driving me crazy...
Thank you in advance :)
Adam
http://www.avhq.com.au/~metrosexuality/ele_pass_conv.JPG
"First, consider Figure 1.5-1a. When the current enters the circuit element at the + terminal of the voltage and exits at the −terminal, the voltage and current are said to “adhere to the passive convention.” In the passive convention, the voltage pushes a positive charge in the direction indicated by the current. Accordingly, the power calculated by multiplying the element voltage by the element current p = vi is the power absorbed by the element. (This power is also called “the power received by the element” and “the power dissipated by the element.”)"
I have read over that paragraph hundreds of times; and still don't understand it... If a positive charge is entering the + terminal of a voltage element, wouldn't the voltage be pushing the charge against the flow of current?
Likewise-
Next, consider Figure 1.5-1b. Here the passive convention has not been used. Instead, the current enters the circuit element at the −terminal of the voltage and exits at the +terminal. In this case, the voltage pushes a positive charge in the direction opposite to the direction indicated by the current. Accordingly, when the element voltage and current do not adhere to the passive convention, the power calculated by multiplying the element voltage by the element current is the power supplied by the element.
If a positive charge is entering the - of a voltage element, wouldn't work need to be done IN the direction indicated by the current to keep the current flowing?
It just doesn't make sense...
Can someone please help clarify this? It's driving me crazy...
Thank you in advance :)
Adam
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