Electronic question plz help!!!?

Question

An electronic circuit consists of 48 decorative 5V lamps all connected in series to a 240V source as shown below.

Lets assume that the circuit worked properly but stopped working after it was moved to anpther location. When plogged in at the new location, all lamps fail to switch on. how i can find out what the problem is ????

Answer 1

Chances are that one of the bulbs in the series chain has failed or become loose in its holder.  (Or the fuse in the plug has blown.  Test that first.)  You could test every bulb in the chain, but there is a quicker way:  a binary search.

Set your trusty AVO on resistance.  Lay out the lights roughly in a straight line.  Disconnect a bulb near the middle of the chain and measure the resistance between each of the bulbholder terminals and each of the plug pins  (4 tests in all:  live pin to base, neutral pin to base, live pin to side, neutral pin to side).

Most probably one of the tests will show continuity, so you now know that there is no fault between that bulbholder terminal and the plug.  (If two showed continuity, you hit the loose / faulty bulb first time.  Lucky!  If none of the tests showed continuity, there is more than one loose bulb.  Replace that one and try another.)

Now you've proved the circuit is sound from one plug pin, through several lamps to one end of the lampholder.  You should be able to determine by simple inspection which way the "good" wire goes and therefore where the fault must lie.  Replace the bulb you removed and remove another one, about halfway in the direction *away from* the known good wiring.

Now this time, the fault will lie either between the bulb you removed last time and the bulb you just removed, or between the bulb you just removed and the plug.  So again, replace this bulb and remove one halfway along the faulty segment.

Doing it this way, you can zero in on the fault quite quickly; because at each stage, you are eliminating half the bulbs.  If only one bulb is faulty, then you should be able to find it within 6 goes.

Answer 2

Try again to plug-in the lamps into an outlet which you  KNOW  works (like test this outlet with a table lamp first).

If it still doesn't work, then one (or even more) of the 48 bulbs is burnt-out, causing the entire serial circuit to be interrupted, hence none of the bulbs will light up.

Now you'll have to find out which of the 48 bulbs is faulty.....

Answer 3

connect alll lamps in parrallel.