DC Circuits and Kirchhoff's Laws Quiz

DC Circuits and Circuit Elements

• Voltage: Electric potential difference between two points, driving current flow. Unit: volts (V).
• Current: Flow of electric charge. Unit: amperes (A).
• Power: Rate of doing work or converting energy. Unit: watts (W).
• Energy: Capacity to do work. Unit: joules (J).
• Open Circuit: No current flow due to a break in the circuit.
• Short Circuit: Unintended low-resistance path causing high current.
• Active Element: Component that can supply energy.
• Passive Element: Component that consumes energy.
• Voltage Source: Example: battery.
• Source Conversion: Changing a voltage source to an equivalent current source, or vice versa.
• Ohm's Law: V = IR (Voltage = Current × Resistance).

Kirchhoff's Laws

• Kirchhoff's Current Law (KCL): Sum of currents entering a node equals the sum leaving it.
• Kirchhoff's Voltage Law (KVL): Sum of voltages in a closed loop equals zero.
• Loop Current Method: Technique for solving circuit equations using closed loops.
• Resistance: Opposition to current flow. Unit: ohms (Ω).
• Temperature Coefficient of Resistance: Rate of change of resistance with temperature.
• Resistance in Series: R = R1 + R2 + ...
• Resistance in Parallel: 1/R = 1/R1 + 1/R2 + ...
• Resistor Applications: Current limiting, voltage division, heating elements.

Inductance and Capacitance

• Inductance: Property of a coil or circuit opposing changes in current flow, generating electromotive force (EMF). Unit: Henry (H).
• Capacitance: Ability to store charge. Unit: Farad (F).
• Inductor VI Relation: V = L dI/dt
• Capacitor VI Relation: I = C dV/dt
• Energy Stored in Inductor: 1/2 L I^2
• Energy Stored in Capacitor: 1/2 C V^2

AC Circuits

• Alternating Quantity: Periodically changing value.
• Cycle: Complete waveform of AC.
• Time Period: Time for one complete cycle.
• Frequency: Number of cycles per second (Hz).
• Amplitude: Maximum value of a waveform.
• RMS Value: Effective value of AC.
• Average Value: Average of all instantaneous values over one cycle.
• Form Factor: RMS Value / Average Value.
• Peak Factor: Peak Value / RMS Value.
• Phase: Angular position of a waveform.
• Phase Difference: Angle by which one waveform leads or lags another.
• Impedance of RLC Circuit: Z = √(R^2 + (XL - XC)^2).
• Resonance: Condition where XL = XC (XL=Inductive Reactance, XC=Capacitive Reactance).
• Resonance Frequency: Frequency at which resonance occurs (f = 1/(2π√(LC))).
• Phase Sequence: Order in which phases reach their maximum.
• Star and Delta Connections: Three-phase connections.

Transformer

• Transformer Principle: Electromagnetic induction.
• Transformer Parts: Core, windings, tank.
• Transformer Types: Core type, Shell type
• EMF Equation: E = 4.44 f Ν φ (f=frequency,N=Number of turns,Φ=Flux)
• Voltage Transformation Ratio: Ratio of secondary to primary voltage.
• Primary Winding: Connected to the input supply.
• Secondary Winding: Connected to the load.
• Mutual Flux: Flux linking both primary and secondary windings.
• Transformer Efficiency: Ratio of output power to input power.
• Core Losses: Hysteresis and eddy current losses.
• Copper Losses: Losses due to resistance in windings.
• Voltage Regulation: Change in secondary voltage from no-load to full load.

DC and AC Machines

• DC Motor Principle: Current-carrying conductor in a uniform magnetic field experiences a force.
• DC Motor Parts: Armature, field winding, commutator.
• Commutator Function: Converts AC to DC in the armature.
• Back EMF: EMF opposing applied voltage.
• DC Motor Types: Series, shunt.
• DC Motor Speed: Determined by back EMF and flux.
• DC Motor Torque: Τ α φ Ιa
• Induction Motor Principle: Electromagnetic induction producing a rotating magnetic field using a three phase AC supply.
• Induction Motor Parts: Stator, rotor.
• Synchronous Speed: Speed of the rotating magnetic field.
• Slip: Difference between synchronous and rotor speed(S = (Ns - Nr) / Ns).
• Applications (DC motors): Cranes, traction systems, lathes, fans.

Measuring Instruments

• MI Instrument (Moving Iron): Electromechanical device measuring AC and DC currents/voltages.
• PMMC Instrument (Permanent Magnet Moving Coil): Electromechanical device primarily used to measure DC current/voltage. Has high accuracy for DC but cannot measure AC.
• Instrument Applications: Power systems, industrial controls, and precise measurements in laboratories.