core 3 - p4 Flashcards
(18 cards)
What is the time constant (τ) for an RC circuit, and how is it calculated?
τ=R×C. Time to reach ~63% of max charge/discharge
Write the formula for capacitor voltage during charging.
Vc (t) = V(1−e ^−t/τ ).
How long does it take for an RL circuit to reach steady state?
Approximately 5τ, where τ=L/R.
Calculate the energy stored in a 10 µF capacitor charged to 100V.
W= 1/2 CV ^ 2 = 0.5 × 10 ^ −5 × 100 ^ 2=0.05J
What is the forward bias voltage for a silicon diode?
~0.7V.
How does a full-wave rectifier differ from a half-wave rectifier?
Full-wave uses both AC half-cycles; half-wave uses only one.
What is the average DC output voltage of a full-wave rectifier with Vpeak = 30V?
V dc =0.636×30≈19.1V.
What does Fleming’s left-hand rule determine?
Direction of force on a current-carrying conductor in a magnetic field (used for motors).
Which rule applies to generators, and what does it determine?
Fleming’s right-hand rule: direction of induced EMF in a moving conductor.
What does the B-H curve represent?
Relationship between magnetic flux density (B) and magnetic field strength (H).
Why does magnetic saturation occur in ferromagnetic materials?
All atomic domains align; further increases in H do not increase B.
State Kirchhoff’s Voltage Law (KVL)
Sum of voltages around any closed loop is zero: ∑V=0.
What is the function of a transistor’s base terminal?
What is the function of a transistor’s base terminal?
How does an NPN transistor differ from a PNP transistor?
NPN: current flows from collector to emitter (base positive). PNP: current flows from emitter to collector (base negative).
What is the typical current gain (β) of a transistor
β = I B / I C, typically 50–300 for small-signal transistors.
How does a residual current device (RCD) work?
Detects imbalance between live and neutral currents (e.g., leakage) and trips the circuit.
Detects imbalance between live and neutral currents (e.g., leakage) and trips the circuit.
Diverts high-voltage surges (e.g., lightning) to ground to protect equipment.
What is the difference between analog and digital signals?
Analog: continuous (e.g., sine wave). Digital: discrete values (e.g., binary 0/1).
