a bulb is rated 220 V , connected to 220 V , 5hz Ac source , will it glow intermittently or will get fused ? and explain too
Answers
Answer:
Hi cheese
Glows intermittently is Right Choice!
Reasons;
Rule out C. There is no reason on earth for it to blow.
Rule out D. There you are giving it 220 volt and so it shall glow.
When you give 5 Hz supply, frequency is too low. Normally when 50 Hz ( 50 times a second AC is given, it will get max volts twice in each cycle, that is it gets varying voltage from 0 to 220 a hundred times a second, in negative and positive cycles), the white hot bulb filament has no time to cool. Hence it appears to us as glowing continuously.
But when you drastically reduce to 5 Hz it has time to cool off and again get white when hot. You will observe the bulb will flash at rate of 10 times per second.
Will it blow out after few cycles?
No, there is no reason. Irrespective of its frequency peak volt is always 1.41 times rms voltage.(This peak is experienced at 50 Hz also). But thermal rating of bulb will not be exceeded as it will average out over larger time base of 200 milliseconds. We must consider the average power which is not dependent on frequency. But if it is too slow as much as 0.1 hz, it may get blown out.