What is the primary function of a resistor?
To limit or control the flow of electric current in a circuit.
You have a 9 V battery and an LED rated for 20 mA at 2 V. What resistor value should you use in series with the LED?
R = (9V - 2V)/0.02A = 350 Ohms
What is the role of a capacitor in a power supply circuit?
To smooth or filter out voltage ripples.
If you need a capacitor to block DC but allow AC to pass, what type of application is this?
Coupling capacitor in signal circuits.
What is the basic function of an inductor?
To store energy in a magnetic field and oppose changes in current.
In a low-pass LC filter, what role does the inductor play?
It blocks high-frequency signals while allowing low-frequency currents to pass.
You need to delay a signal slightly before it reaches another stage. Which passive component configuration can you use?
An RC delay circuit (resistor + capacitor).
Your radio receiver is picking up too much noise. Which passive component network can help?
An LC filter (inductor + capacitor tuned to the desired frequency).
What happens if you connect resistors in series?
Rtotal = R1 + R2 + …
What happens if you connect resistors in parallel?
1/Rtotal = 1/R1 + 1/R2 + …
You need a 1 kΩ resistor, but you only have 2 kΩ resistors. How do you achieve it?
Put two 2 kΩ resistors in parallel.
What happens if capacitors are in parallel?
Ctotal = C1 + C2 + …
What happens if capacitors are in series?
1/Ctotal = 1/C1 + 1/C2 + …
You want to build a 100 µF capacitor but only have 47 µF ones. How do you get close?
Put two 47 µF in parallel = 94 µF (close enough).
What does a transformer do?
Transfers electrical energy between circuits through magnetic induction, changing voltage/current ratios.
A transformer has a turns ratio of 10:1 and is fed with 230 V AC. What is the secondary voltage?
230/10=23V AC
Why are transformers not used in DC circuits?
Because transformers rely on changing magnetic flux (AC), DC produces no changing flux.
What is the function of a fuse?
To protect circuits by melting when the current exceeds a safe limit.
If a circuit normally draws 1 A, what fuse rating should you choose?
Slightly higher, e.g., 1.5 A fuse.
Formula for Ohm’s Law?
V = I⋅R
Formula for charge stored in a capacitor?
Q = C⋅V
Formula for impedance in rectangular form?
Rectangular: Z = R + jX
Formula for capacitive reactance?
Xc = 1/(2πfC)
Formula for inductive reactance?
Xl = 2πfL
