Calculating power with a wattmeter

Thread Starter


Joined Mar 23, 2009
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 ?



Joined Nov 30, 2010
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.


Joined Feb 4, 2008
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.