Battery draining in resistive circuit

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SUMMARY

The discussion centers on the impact of volume control on battery life in resistive circuits, specifically in transistor radios. It concludes that lowering the volume does indeed prolong battery life, as the volume control functions as a voltage divider, reducing the power drawn by the amplifier. This means that less sound output results in lower power consumption from the battery, contrary to the initial assumption that increased resistance merely dissipates energy as heat. Understanding Ohm's Law and power definitions clarifies this counterintuitive relationship.

PREREQUISITES
  • Understanding of Ohm's Law
  • Knowledge of power calculations in electrical circuits
  • Familiarity with voltage dividers
  • Basic principles of audio amplification
NEXT STEPS
  • Research the principles of voltage dividers in electronic circuits
  • Learn about power consumption in audio amplifiers
  • Explore the relationship between resistance and power in DC circuits
  • Investigate battery chemistry and its impact on performance in low-power devices
USEFUL FOR

Electronics enthusiasts, audio engineers, and anyone interested in optimizing battery life in resistive circuits.

Dark Maggot
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When I was a kid listening to a transistor radio under my pillow late at night I used to wonder whether turning the volume down low would delay the gradual loss of battery voltage. My doubts centered in the fact that the volume control was (at least in those days) a variable resistor. I reasoned that turning down the volume (increasing the resistance) would merely dissipate more EMF in the form of heat, so that the actual work done by the DC cell would be insensitive to changes in the volume setting.

What's the truth of the matter: would listening at low levels prolong useful battery life? If so- where was my childish reasoning faulty?
 
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Welcome to PF! Are you familiar with ohm's law and the definition of power? If you apply them to this situation you may find something counerintuitive about the relationship between resistance and power...
 
Your conclusion was right, but not for the reason you suggest.

The volume control let's you choose how much signal is used to drive the speaker amplifier of the radio. It does this by voltage divider action.

These amplifiers take more power from the battery when they are producing more sound output, so they will use up the battery more quickly if they are delivering more sound.
 

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