core 3 - p2 Flashcards
(20 cards)
What is electrical energy, and how is it measured commercially?
Energy derived from charged particles’ movement. Sold in kilowatt-hours (kWh):
1 kWh = 3.6 MJ
What equation links electrical energy, power, and time?
Energy = Power × Time.
Define electrical power and state its SI unit.
Rate of energy transfer. Unit: Watt (W), 1W = 1J/s.
Write the three formulas for power in terms of V, I, and R
P = V × I, P = I ^ 2 × R, P= V ^ 2/ R
What is a lumped network? Give an example.
Components (resistance, inductance, capacitance) are physically separable. Example: Transmission line.
How does a linear network differ from a non-linear network?
Linear: R , L , C remain constant (e.g., resistor). Non-linear: Values change with conditions (e.g., diode).
What defines a bilateral network?
Voltage-current relationship is unchanged if current direction reverses (e.g., transmission line).
Distinguish between active and passive networks
Passive: No internal energy source (resistors, capacitors). Active: Contains energy sources (batteries, transistors).
Define capacitance and its unit
Charge stored per volt: C= Q / V. Unit: Farad (F).
What factors determine the capacitance of a parallel plate capacitor?
C = εA / d (depends on plate area A, distance d, permittivity ε).
List two types of capacitors and their typical uses.
Electrolytic (power supplies), Ceramic (general usage).
Name three non-sinusoidal waveforms.
Square, triangular, sawtooth.
Which waveform in Figure 1.97 is marked with an [x]?
Triangular wave.
Define magnetic flux (Φ) and flux density (B)
Φ: Total magnetic field lines (unit: Weber ). B=ΦA(unit: Tesla).
What is magnetomotive force (MMF)?
Fm = N × I (product of coil turns and current). Unit: Ampere (A).
State Faraday’s Law of electromagnetic induction.
Induced EMF is proportional to the rate of change of magnetic flux: E = −N ( dΦ / dt )
What does Lenz’s Law state about induced current direction?
Induced current opposes the change in flux causing it.
Write the formula for EMF induced in a moving conductor.
E=B×L×v ( B: flux density, L: length, v: velocity ).
Define self-inductance ( L ) and its unit.
Property where changing current induces EMF in the same circuit. Unit: Henry (H). Formula: L= NΦ/ I
How does a transformer work?
Uses mutual inductance: AC in primary coil induces EMF in secondary coil. Voltage ratio = turns ratio: V1/V2=N1/N2
