Voltage divider or Transverse current

[tahir4awan]

Hello,

On Friday we received an assignment. The calculation was not a problem but the theory behind it was confusing. My teacher showed me two circuits arrangements. In one only series resistor was used and in other voltage divider was used. The radio was working good only in voltage divider circuit because it was stable.

The radio was using 6V. The problem with this is, the more current will flow through R2. I mean, when you change the volume to high, it will require more current to generate more sound. Secondly if you change the resistance of the radio, which is parallel with R2, then the overall resistance will be changed, and hence we have too low voltages. So how come this voltage divider is working, while radio need constant 6V? Also a term q is used. Which should be more than 5 to achieve stability.

Thirdly, I have not noticed it before, but what changes the Potentiometer (volume). Because it has positive resistance, which means if you turn, it will create more resistance, but we have more sound.

Any help from someone.


Thanks

 

[KlausST]

Hi,

6V surely does not need to be perfectly constant.
It will vary with load current.
But the higher Iq the lower the variation.

According the given information it is expected that with Iq >= 5 × IL the voltage to be fairly constant.

Klaus

 

[tahir4awan]

Hi,

6V surely does not need to be perfectly constant.
It will vary with load current.
But the higher Iq the lower the variation.

According the given information it is expected that with Iq >= 5 × IL the voltage to be fairly constant.

Klaus

Does not we need constant voltage in electronics devices? I mean the power supply and batteries provide constant voltage.

Secondly what causes potentiometer (volume) of a radio, if we increase volume?

 

[KlausST]

Hi,

Does not we need constant voltage in electronics devices?

What do the datasheets say?
Every device has a "range" of recommended operating voltage.

Ask yourself what do you understand by "constant" voltage.
Is 6.0000V good and 6.0001V bad?
Nothing is absolutely constant or accurate.

But some devices are happy with a wide range other devices need a narrow range. Thus it's urgent to read datasheets.

In your case the task says "Iq >= 5 × IL" is good enough. Thus you need to keep or rely on this information.

Klaus

 

[wwfeldman]

Secondly what causes potentiometer (volume) of a radio, if we increase volume?

when you turn the volume knob, you are (likely) turning a potentiometer, which changes the amplification,
so the volume goes uop or down, depending in what direction you turned the potentiometer.

how this works depends on the design of the amplifier

 

[Audioguru]

A radio draws a lot more than only 10mA, it might draw 10mA to 166mA which varies with the output loudness so a voltage divider is never used to power it. Its battery is 6V when playing softly and is maybe 5.7V when playing loudly.

A volume control load (the amplifier input) has a very low current so the volume control divides the audio signal level properly.