Data Sheet

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24. Simulation of a PTC-fused Lamp

Build the circuit to the left and turn ON the switch (62).

The LED (69) will glow red simulating the PTC fuse is warm.

Pretend the magnet (7) is a piece of ice and place it near the

reed switch (83). The PTC fuse cools down, allowing current

to ow and the lamp (76) to light.

25. Fused Motors

Replace the lamp (76) with the motor (95). Some motors

have fuses that pop-out when they are triggered. Move the

magnet (7) away from the reed switch (83) to simulate a fuse

that has popped, making the motor (95) spin more slowly.

Simulate resetting the fuse by moving the magnet back next to

the reed switch (83). Motors are designed with fuses to limit

the current that can be seen by the motor to prevent res.

26. Ohm’s Law Revisited

Build the circuit to the left. Press the switch (62), the lamp

(76) will turn on very dimly and the motor (95) will turn on at

the same time. Remove the motor resistance by pressing the

press switch (61) and the lamp (76) will become brighter. Per

Ohm’s Law, given the same voltage (4.5V), a lower resistance

in the circuit leads to a larger current in the circuit which is why

the lamp (76) gets bright when you press the press switch (61).

27. Magnet Does Two Jobs

Replace the press switch (61) with the reed switch (83), by using

the magnet (7) you can control the brightness of the lamp (76)

and turn the motor (95) OFF at the same time. You may have

noticed that the magnet (7) can be attracted to the motor (95).

This is because motors have magnets inside to create a magnetic

eld that spins the motor when current ows through the motor.

1st level