Testing Room Heater Coil

You used up all the electricity in the first half of the coil, so there's nothing left to make the tester glow.

The rest is magic.

but if whole of energy is being used up in first half how the second half is getting heated up too ??

Does the coil have any support brackets, maybe one in the middle? Is the coil shorting out at the support bracket?

no coil is totally insulated inside earthen cast and there are no support brackets

Following your descriptions, the heater assembly seems to have 2 separate heater coils as you call it? It is possible you have a control switch with 2 settings; A) Max or high heat - where both heating elements are powered and B) normal - where only one is being powered? Another scenario is your heater has thermostat controls for each heating elements and the thermostats are set for two different temperatures?

Question #2 - Using the metal casing as a test reference - while you can get a good electrical indication while doing your test - it is likely the metallic case is electrically grounded. It is done that way for safety reasons and to prevent anyone from getting shocked.

If only one heating element is working (power ON), you may have a thermostat problem. A bi-metallic switch that controls the heating element(s)? Look for the thermostat(s) - commonly used type are the bi-metallic which are cheaply made and therefore very fragile.

no heater has just a single coil and none of switch mentioned by you

its just a simple room heater with single coil with only proximal part of coil making tester glow

actually i was thinking that part of electrical energy is being dissipated as heat energy across the length of coil and at some point current or voltage difference is too low to be detected by a tester

is that could be plausible explanation??/

Is the heater coil similar or looks like the heating element in your electric stove?

yes

Then it is possible the nichrome wire inside that coil is partly touching (shorted) to the coil body and therefore will longer exhibit getting fully red hot? Due to a partial short, it is still consuming some electrical energy producing low heat but not enough to be visible, as in red hot! Take the heater inside a very dark room and observe. Also, be very careful not to burn yourself!

It sounds like you have a broken heating element. The only sure way to check the element is to check continuity and rated resistance. Just be careful and make sure the power is off before you do any resistance or continuity tests

Depending on the tester you're using you can get false positive and false negative readings. Use a voltmeter with a 'Lo Z' option.

Sounds like you are using a common neon glow bulb type power tester. The bulb takes about 60 - 100 volts at minimum to light up which is probably why it only works about half way down your heating element. After that the voltage is too low for that type of simple tester to work.

The power supply end is at the highest voltage and the ground end its zero with a proportional drop resulting all the way along the element itself.

I tried to tell him that here: 1

Sorry I am not good at reading between the lines on magical mystery references.

Just ask my wife about it I don't get most of what she talks about relating to her belief systems.

Have you tried referencing your tester from the live side to the element (unless you are using one of those "floating" no-contact testers)? I suspect that you will discover that it is symmetric, with your tester glowing when touched to the low side and anywhere up to around the halfway point. As someone has already said; the voltage drop along the element will eventually prevent your neon tester from glowing. From either end [live or ground] you will be able to make it glow when connected to the far half.

Along the element (coil) there is a continuously changing voltage relative to each end. You need more than half of that voltage to start the neon. In another test, touching two spots, one at about the 1/4 mark, and the other near the 3/4 mark, should also make it glow, since the difference is about half of the total voltage.

Please be careful; your post doesn't make it appear that you are very experienced about electricity, and it CAN be dangerous.

What you are witnessing jaswal is avoltage divider in action.

can you make me understand voltage divider in simple physics as i cant understand formulas given on wiki...

actually i m a doctor with just basic knowledge of physics

The heater element is a "long" resistor.

The total resistance of the element is the sum of the incremental resistance along its length.

Rtotal = R1 + R2 + R3 + ..... Rn

If in doubt, consult a qualified electrician.

Touch it with your bare finger and see if it is hot! Lyn is right if it is a "cal rod" it may be shorted out at any point or support.