how to calculate power in circuit

Thread Starter

aryna

Joined Dec 10, 2020
19
hi everyone , im very confuse with this circuit, i need to calculate P=IV, in this circuit it shows many current and, is it correct if i took current from VDD
i understand that for using P=IV, the voltage from power supply is V=8V, and my question is it correct if i took current from VDD, or i need to add all the current from all component?
1610014278424.png
 

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ericgibbs

Joined Jan 29, 2010
13,219
hi a,
Downloaded your files.
The power supply connections don't make any sense.?
Why have you used two labels for each supply.?

I will edit and run and post back.
E
 

ericgibbs

Joined Jan 29, 2010
13,219
hi aryna,
As this is Homework I can only guide you thru the problem, not give you the final answer, OK.
So could you first redraw your circuit like this image, then we can do the next step.
E
 

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Thread Starter

aryna

Joined Dec 10, 2020
19
okay i get it, but why the value of power become negative for V3= -0.0540892, and may i ask a little bit explanation of this
.meas TRAN arg1 AVG (I(V3)*V(pv))
And why mine like this

1610031134660.png
 

Thread Starter

aryna

Joined Dec 10, 2020
19
so basically the power is negative because the current negative? can you explain to me why? is it correct to measure power consumption in is P = I(Vdd)*V(vdd)
 

ericgibbs

Joined Jan 29, 2010
13,219
hi,
.meas TRAN arg1 AVG (I(V3)*V(pv))

This is explained in the Help files. measure,
TRAN for analysis method
arg1 is a name for a Variable
AVG is the Average value
of I(V3) * V(pv)

How do you get a run time of 5.4 seconds .???
AAA 1011 14.55.gif
it should be
AAA 1012 15.04.gif
Your power values are much to high,,, ~ 7 Watts is wrong,

LTSpice chooses the direction of the current so it may sometimes give a negative value, for power it must be positive.

Look at this and double check.
 

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