Calculating power with a wattmeter

Thread Starter

nyasha

Joined Mar 23, 2009
90
I calculated the power for this circuit and got a positive value of 1100 watts. However in the textbook they have the solution being negative. Can someone please tell me why ?

 

#12

Joined Nov 30, 2010
18,159
One point of view is that a negative amount of power means the circuit is absorbing 1100 watts of heat from the surrounding air. This being impossible, I thing the book is wrong. Typographical error.
 

mik3

Joined Feb 4, 2008
4,843
The winding for measuring the voltage (bottom one) has its dot to the right. This means that it measures a negative voltage (or 180 degrees phase shifted) which gives a negative power.
 
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