Hi Haribabu,

Anytime you accelerate and electric charge you will produce electromagnetic radiation (EMR). And accelerate means any change in velocity. Since velocity is a vector quantity, acceleration not only includes changing its magnitude (speed), but also it's direction. The more acceleration you have, and the more charge that's involved, the more EMR you will produce.

Since acceleration is dv/dt, you can increase the amount of acceleration by increasing the dv (change in velocity) or by decreasing the dt (the time it takes). Conversely, if you lower the change in velocity, or increase the time it takes, you will decrease the acceleration, and by extention the amount of EMR produced. You can also increase the EMR by increasing the current, or vice versa.

In your case you pretty much have the minimum dt since contact is made practically instantaneously. So to vary the amount of EMR you produce, you will need to vary the current. Interestingly, an inductor would actually slow down (reduce the dt) the change in current and thereby reduce any EMR production. While the unimpeded contacts would produce the most EMR, it would be extremely short lived. Impeding the current, on the other hand, would reduce the EMR produced but it would last longer (until the current stabilized). Of course, this is assuming a steady DC current is ever reached. If this is an AC current, then everytime the direction changes, more EMR is produced.

Finally, even in a steady DC state, if the current is changing directions it will produce some EMR. So one way to produce a controlled amount of EMR would be to force a current (AC or DC) through a coil of wire. The more current you push the more EMR you produce. Also, the smaller the radius of the winding (which is to say the greater the acceleration) the more EMR you'll produce.