Data Sheet

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26. Electronic Efciency

Electronic Efciency is dened as the Useful Power Output divided

by the Total Power Input. Build the circuit shown on the left and

press the switch (62). The star LED (70) will light, but the lamp

(76) will not light brightly. There is resistance built into the star

LED (70) to protect it (too much current could damage an LED),

and this resistance is limiting the current in the circuit. Yet this

circuit shows that the star LED (70) is more efcient than the

lamp (76) because it still produces light (useful output power)

even at the lower current.

27. Inertia

Build the circuit shown on the left and place the fan (60) on the

motor (95). Press the switch (62) and the star LED (70) will

light up and the fan (60) will start spinning. Turn OFF the switch

(62) and the fan will keep spinning for a little while, but the star

LED (70) will turn off immediately. This circuit demonstrates the

concept of Inertia: a property of matter by which it continues

in its existing state of rest or uniform motion in a straight line,

unless that state is changed by an external force. The motor

(95)/fan (60) has inertia but the star LED (70) does not.

WARNING: Moving parts. Do not touch

the fan or motor during operation. Do

not lean over the motor.

2nd level