Because when exercising your heart pumps more blood to your body and
it has more space to fill so it beats faster
The coronary<span> arteries are the network of blood vessels that carry oxygen- and nutrient-rich blood to the cardiac muscle tissue. The blood leaving the left ventricle exits through the </span>aorta<span>, the body's main artery.</span>
In cartography, a contour line<span> joins points of equal elevation (height) above a given level, such as mean sea level. A </span>contour map <span>is a </span>map<span> illustrated with </span>contour lines, for example atopographic map<span>, which thus shows valleys and hills, and the steepness of slopes. </span>
Electromagnets can easily be turned on and off.
Explanation:
An electromagnet produces magnetic field which is done by the electric current. These electromagnets contain a wire would like a coil. The current passes through the wire and the magnetic field is concentrated in the center which is the "center of the coil".
When the current is "turned off" the magnetic field "disappears". This shows that we have can have a control over the passage of current or the magnetic field. Thus, the "main advantage" of the electromagnet is that it can be easily turned on and off whenever necessary.