Rechargeable Bicycle Light
Electric Circuit Analysis Question?
A bicycle LED headlight requires 5V, 250mA to operate. Using Ohm’s law, determine the equivalent resistance of the light. What is the power consumption rate in W? How many electrons pass through per second? It is powered by four AA rechargeable batteries in series. Each battery provides 1.25V and has a specification of 2300mA-Hour. How many seconds would the battery last?
I figured out the first 2 parts:
R = I/V = 50kOhm
P = VI = 1.25W
I just need some help with the last two questions:
How many electrons pass through per second? It is powered by four AA rechargeable batteries in series. Each battery provides 1.25V and has a specification of 2300mA-Hour. How many seconds would the battery last?
A bicycle LED headlight requires 5V, 250 mA to operate.
Using Ohm’s law, determine the equivalent resistance of the light.
250 mA = ( 250 mA )( 1 A / 1000 mA ) = 0.25 A
R = ( 5 V ) / ( 0.25 A ) = 20 Ω
What is the power consumption rate in W?
P = ( 5 V )( 0.25 A ) = 1.25 W
How many electrons pass through per second?
( 0.25 A ) = ( 0.25 C/s )
( 6.242 × 10^18 electrons/C )( 0.25 C/s ) = 1.560 × 10^18 electrons/sec
It is powered by four AA rechargeable batteries in series.
Each battery provides 1.25V and has a specification of 2300mA-Hour.
How many seconds would the battery last?
( 4 battery )( 1.25 V/battery ) = 5 V
With four 1.25 VDC 2300 mA-Hr batteries in series, effectively it is one 5 VDC 2300 mA-Hr battery.
At the beginning of the problem it stated, “the headlight requires 5 V 250 mA to operate”, thus,
( 2300 mA-Hr / 250 mA )( 3600 Sec/Hr ) = 33,120 Sec
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