Detector Building C

[pikachu4919]

2022 Question Marathon Thread for Detector Building C.

Question Marathons Explained

[ThomasL]

Let's start!
1. What does LED stand for?
2. You have a circuit with a 9V battery in series with a resistor and an LED (forward voltage drop of 3.3V). If the desired current in the circuit is 10 mA, what resistor value should you choose? (Assume LED is forward-biased)

[RiverWalker88]

Let's start!
1. What does LED stand for?
2. You have a circuit with a 9V battery in series with a resistor and an LED (forward voltage drop of 3.3V). If the desired current in the circuit is 10 mA, what resistor value should you choose? (Assume LED is forward-biased)

It's been long enough! I'll give this a try.

Click to Show Answer

1. LIGHT EMITTING DIODE
2. So, we subtract the LED voltage drop to get the voltage drop over the resistor (9V-3.3V=5.7V). Then we use that voltage and the current of 10mA to calculate the resistance of 570 ohms.

1. In my detector, I placed a resistor in series with the probe, and measure the voltage drop before that resistor. What is the fixed resistor called and what is its purpose?
2. As the salinity of a solution increases, the conductivity _____, which implies that the resistance _____, and the voltage drop _____. (Fill in each blank with increases/decreases)