Flashlight battery polarity (mixed) ?

[Capiert]

Voltage addition?

 

If 1 (1.5 V) battery

 of a 3 battery flashlight

 is wrong (=the opposite (polarity))

(then) the total voltage is zero, not 1.5 V

 so the lamp (filament)

 will NOT go on (=won't light)

 when the switch is closed (=turned on).

 

Kirchhoff's voltage law

 adds voltage( drop)s

 on loads,

 but seems to collapse

 when dealing with (battery) sources

 of mixed polarity.

 

(=I find that (unexpectedly) rather (stunningly) peculiar,

 the math fails!)

 

Can anyone help me to (simply) understand

 what's happening,

 (e.g. with like charges repel, unlike attract)

 why the voltages do NOT add anymore

 (for mixed polarity batteries)?

 

E.g. total voltage (of batteries) adds for same polarities

Vt=V1+V2+V3

4.5 V = 1.5 V + 1.5 V + 1.5 V, &

-4.5 V = -1.5 V - 1.5 V - 1.5 V,

 but (makes no sense with mixed polarities)

0 V # 1.5 V + 1.5 V - 1.5 V, &

0 V # 1.5 V - 1.5 V + 1.5 V, &

0 V # -1.5 V + 1.5 V + 1.5 V, &

0 V # -1.5 V - 1.5 V + 1.5 V, &

0 V # -1.5 V + 1.5 V - 1.5 V, &

0 V # 1.5 V - 1.5 V - 1.5 V.

Edited November 12, 2017 by Capiert

[EdEarl]

Mixed polarities are summed as all numbers are summed (0 = +1.5 - 1.5)

1.5 V = 1.5 V + (1.5 V - 1.5 V), &

1.5 V = 1.5 V - 1.5 V + 1.5 V, &

1.5 V = -1.5 V + 1.5 V + 1.5 V, &

-1.5 V = -1.5 V - 1.5 V + 1.5 V, &

-1.5 V = -1.5 V + 1.5 V - 1.5 V, &

-1.5 V = 1.5 V - 1.5 V - 1.5 V.

[studiot]

Have you actually tried this experiment?

It is very instructive and proves Ed correct +1

 

Here are two photos of actual measurements.

I am using slightly exhausted 1.2 volts cells so their combine voltage only adds up to 3.5 volts

The first has all three batteries in series in the same direction.

I have reversed one of the batteries for the second shot and you can see the voltmeter reading just under 1.2 volts.

[Strange]

2 hours ago, Capiert said:

If 1 (1.5 V) battery

 of a 3 battery flashlight

 is wrong (=the opposite (polarity))

(then) the total voltage is zero, not 1.5 V

Why do you think it is zero?

[koti]

2 hours ago, studiot said:

Have you actually tried this experiment?

It is very instructive and proves Ed correct +1

 

Here are two photos of actual measurements.

I am using slightly exhausted 1.2 volts cells so their combine voltage only adds up to 3.5 volts

The first has all three batteries in series in the same direction.

I have reversed one of the batteries for the second shot and you can see the voltmeter reading just under 1.2 volts.

What are you using those D cells for studiot? If it's a flashlight you must get rid of it asap and get a new one running Li-IOn's

[studiot]

They came out of my digital(DAB) radio recorder. This is the only model I know of that records DR, expensive but it does have design issues.

Edited November 12, 2017 by studiot

[Endy0816]

Might be a diode in the circuit.

[koti]

6 hours ago, studiot said:

They came out of my digital(DAB) radio recorder. This is the only model I know of that records DR, expensive but it does have design issues.

I see. What do you use it for? Whats "recording DR" ?
 

[studiot]

It records radio programs (or auxiliary audio inputs) directly onto an SD card, and provides a pause-the-radio-to-answer the-phone function or a listen at another time function.

The set normally runs off the mains, but the batteries are handy to take it into the garden. Roberts, the makers, didn't think to make it rechargeable.

In fact all the DAB radios I have seen have suffered clumsy and inept design.

DR is digital broadcast radio. DAB is the format used in the UK

Edited November 12, 2017 by studiot

[Capiert]

10 hours ago, studiot said:

Have you actually tried this experiment?

Way back (long ago)

 & (I) was confused

why the lamp didn't light at all.

I didn't measure the voltage (with a digital meter)

 like you.

Your answer helps a lot

 with the fotos.

Quote

It is very instructive and proves Ed correct +1

 

Here are two photos of actual measurements.

I am using slightly exhausted 1.2 volts cells so their combine voltage only adds up to 3.5 volts

The first has all three batteries in series in the same direction.

I have reversed one of the batteries for the second shot and you can see the voltmeter reading just under 1.2 volts.

 

9 hours ago, Strange said:

Why do you think it is zero?

Because back then the lamp

 didn't light at all

 so I thought years later

maybe a diode effect happened.

But you're right,

 most of the flashlights (I had used) back then were 2 cells (occationally 3).

Studiots fotos are very convincing (=helpful).

8 hours ago, koti said:

What are you using those D cells for studio?

Yes. I used to play around with the batteries.

Quote

If it's a flashlight you must get rid of it asap and get a new one running Li-IOn's

Good tip. I'll keep it in mind.

Right now I only find LED flashlights, also often with 3 cells

 but they only work 1 way because of the LEDiode.

Thanks everybody.

You've helped a lot

 & got me thinking (right (again), hopefully back on track).

If I get a chance someday

 I can try to measure.

Edited November 12, 2017 by Capiert

[Externet]

It is different to say 'the flashlight does not turn on' and 'the voltage is zero'

A LED will not turn on with only 1.5V.  Needs to be supplied with more than its Vf.