It seems like it should just stop immediately when the flow of electricity is cut off. I was hoping someone could tell me more about the physics (of radio waves and/or electricity) that are involved.
2007-09-08 12:50:12 · 9 answers · asked by guiderock 2 in Science & Mathematics ➔ Engineering
You are describing a radio that is powered by AC power
from a wall outlet. All such radios have an internal power
supply that converts the AC to DC that is required by the
circuits inside the radio. The power supply has capacitors
that store up a small electric charge, and when the power
plug is pulled, it takes a short time to drain this remaining
charge from the capacitors. This stored charge is what
causes the radio to run on for a short time after the plug
is pulled.
2007-09-08 13:34:13 · answer #1 · answered by Reginald 7 · 3⤊ 0⤋
The radio does not work on line current. That voltage has to be changed to DC for the electronics to work. The conversion to DC voltage(s) includes a storage function which is the capacitor mentioned. You might not notices, but the radio does not come on immediately when plugged in either. This delay is shorter because the power supply can deliver more current to charge up the capacitor than the radio will draw off in normal operation.
Old style vacuum tube radios that did work directly off the line would often fail if plugged back in while the filaments were still hot. The current that the reservoir capacitor could draw off the line was normally limited while waiting on the filaments to warm.
FYI your kitchen toaster elements will stay red hot for a few seconds after you pull the plug on that as well. Pulling the plug on operating electrical equipment is not safe. Appliances with motors can cause a back flow of current that can cause a significant arc.
2007-09-09 13:23:34 · answer #2 · answered by lare 7 · 0⤊ 0⤋
A radio does not use much power
so the storage capacitors in the supply rails
(large enough to prevent hum (50/60 Hz) )
A lot of appliances are like this
you'll think an appliance has not responded
to the on/off switch because the green Led is still on
2007-09-09 07:51:14 · answer #3 · answered by Anonymous · 0⤊ 0⤋
It only means that there is a big capacitor installed in your radio. The larger the capacitor, the higher the voltage stored on it. The time it takes to let the radio ON would depend on the time constant of your circuit. The time constant is equal to RC for an RC circuit.
2007-09-09 08:46:59 · answer #4 · answered by ptolemy862000 4 · 0⤊ 1⤋
The power supply contains capacitors that store energy to filter variations in voltage. Those capacitors are what are providing the energy that is keeping the radio on.
2007-09-08 22:43:46 · answer #5 · answered by Rich Z 7 · 2⤊ 0⤋
Stored charge in the capacitors. They take several seconds to bleed off after removing power.
2007-09-08 21:44:23 · answer #6 · answered by T L 2 · 1⤊ 0⤋
the load resistance of the transformer secondary has one or more stages of capacitors in parallel......these capacitors store charges...when the supply is cut off,these discharge..and it takes a finite time to discharge depending on the load resistance(RC time constant)..it is during this time the radio continues to run after the power failure
2007-09-08 22:42:31 · answer #7 · answered by 621 3 · 1⤊ 0⤋
There is some residual current stored in components such as capacitors that take a moment to drain after the source current is removed.
2007-09-08 20:00:14 · answer #8 · answered by gunplumber_462 7 · 1⤊ 2⤋
there is a big capastor 1000 muf
2007-09-08 21:42:25 · answer #9 · answered by JAMES 4 · 0⤊ 2⤋