A wildlife telemetry transmitter contains an infrared LED, a control switch, and a battery pack.
Write down the equation which links charge flow (QQQ), current (III), and time (ttt).
The transmitter was operated continuously for 14 hours14\text{ hours}14 hours. The current through the LED was 85 mA85\text{ mA}85 mA. Calculate the total charge flow through the LED during this period.
When replacing the battery pack, a technician installed it with the polarities reversed. Explain why the transmitter's LED failed to light up.
Write down the equation which links efficiency, total power input, and useful power output.
The total power input to the LED is 0.75 W0.75\text{ W}0.75 W. The efficiency of the LED is 0.840.840.84. Calculate the useful power output of the LED.