why is it a ship sailing in a straight line at a fixed velocity creates waves on the shore, but dc current with a fixed value cannot create an EM wave?
In: Physics
That is a very intelligent observation!
There is one important difference.
A ship sitting in a lake raises the level of the lake, but creates no waves. Once it starts moving it creates waves.
A wire with a static current creates no waves, **but if you move the wire the EM waves appear!**
The proper analogy to a moving ship is a moving wire.
I would say the ship is like a rising edge, like turning on a DC supply. Would a long pipe sliding through the water make a wave?
Imagine you have a toy boat moving in a straight line in a bathtub at a steady speed. As it moves, it pushes the water around it, creating waves that travel all the way to the edge of the tub.
Now, think about electricity like water. When you have DC (direct current), it’s like the water in a hose flowing steadily in one direction. Since the flow is constant and doesn’t change, it doesn’t create ripples or waves in the water.
Waves on the shore are created by changes and disturbances in the water. Similarly, electromagnetic (EM) waves are created by changes or disturbances in electric and magnetic fields. With AC (alternating current), the current is constantly changing direction, creating these disturbances and generating EM waves. But with DC, since the current is steady and unchanging, there are no disturbances to create EM waves.
So, just like a steady flow of water in a hose doesn’t create ripples, a steady DC current doesn’t create EM waves. It’s the changes and fluctuations that are key to creating waves, whether in water or in electromagnetic fields.
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