Learning module
Resistors
Resistors limit current, divide voltage, set bias points, and turn electrical energy into heat.
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Mark lessons as complete as you work through the bench checks, then use the quiz to test the ideas.
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Current lesson
Resistors
AC vs DC
DC flows one way. AC changes direction repeatedly and is used for power distribution.
Resistors
Resistors limit current, divide voltage, set bias points, and turn electrical energy into heat.
Capacitors
Capacitors store charge, smooth supplies, pass changing signals, and block steady DC.
Inductors
Inductors store energy in magnetic fields and resist changes in current.
Transformers
Transformers transfer AC energy through magnetic coupling and change voltage by turns ratio.
Amplifiers
Amplifiers use a small signal to control a larger signal for audio, sensors, and communication.
Speakers
Speakers use a voice coil in a magnetic field to move air and create sound.
Radio Waves
Radio uses electromagnetic waves to carry information through space.
Solar Basics
Solar panels provide variable DC power that needs regulation before charging batteries.
Start here
Make a 12 V LED circuit and choose a resistor for about 10 mA to 15 mA, then confirm it in the Ohm's Law calculator.
Key ideas
A resistor opposes current flow and drops voltage according to Ohm's Law.
Series resistors add directly. Parallel resistors create a lower equivalent resistance than the smallest branch.
Resistors dissipate heat, so wattage rating matters as much as resistance value.
Voltage dividers are useful for signals and references, but they are poor power supplies for heavy loads.
Useful formulas
V = I x R
P = I^2 x R
Series: Rtotal = R1 + R2
Divider: Vout = Vin x R2 / (R1 + R2)
Bench checks
Measure resistance with power disconnected.
Calculate expected current before powering an LED.
Touch-test only after power is removed; hot resistors are a clue the wattage is too low.
Common mistakes
Forgetting the LED current-limiting resistor.
Using a tiny resistor where the power dissipation needs a larger body.
Reading resistor colour bands without checking tolerance or meter value.