how do i find out if my tensorflow application uses the GPU?

Hi there
how do i find out if my tensorflow application uses the GPU?
In the Task Manager, the GPU is at 0%. Is there another ad? Or is Tensorflow really not using the GPU? How can I find out why?
I have:
pip.exe install tensorflow-gpu == 1.15
installed and fun like
with tf.device (’/ GPU: 0’):
are available in the code …
I’m really desperate. I have a Geforce GTX 1080 Ti.