The unit of electric current is **ampere (A)**. One ampere represents the flow of one coulomb of charge per second.
What is the basic unit of voltage?
A Ohm
B Ampere
C Volt
D Joule
The unit of voltage is **volt (V)**. It is defined as the potential difference that will cause one ampere of current to flow through a resistance of one ohm.
Which of the following describes the behavior of a purely resistive circuit in AC?
A The voltage and current are out of phase by 90 degrees.
B The voltage and current are in phase.
C The current lags the voltage by 90 degrees.
D The voltage and current are unrelated.
In a purely resistive circuit, the **voltage and current are in phase**, meaning they reach their maximum and minimum values at the same time.
What does the term “transient analysis” in electrical circuits refer to?
A The study of a circuit’s behavior in steady-state conditions.
B The study of a circuit’s behavior when a sudden change in conditions occurs.
C The study of the voltage drop across resistors.
D The calculation of power in AC circuits.
**Transient analysis** involves analyzing a circuit’s behavior when it is subject to sudden changes, such as when a switch is turned on or off.
What does the term “steady-state analysis” refer to in electrical circuits?
A The study of short circuits.
B The study of long-term behavior of a circuit.
C The study of behavior during sudden changes.
D The analysis of digital circuits.
**Steady-state analysis** refers to the long-term behavior of a circuit after transient effects have settled, such as when the voltages and currents become constant.
What is a phasor in an AC circuit?
A A time-domain representation of current.
B A vector that represents a sinusoidal function in the frequency domain.
C A representation of voltage as a sinusoidal waveform.
D A capacitor in an AC circuit.
A **phasor** is a complex number that represents a sinusoidal waveform. It is used to simplify the analysis of AC circuits by converting sinusoidal voltages and currents into complex numbers.
What is the resonance condition in an RLC circuit?
A The inductive reactance equals the capacitive reactance.
B The total resistance equals zero.
C The current is minimized.
D The capacitor is fully discharged.
**Resonance** occurs in an RLC circuit when the inductive reactance equals the capacitive reactance. This minimizes the impedance and maximizes the current in the circuit.
Which of the following is true for a series circuit?
A The total current is divided among the components.
B The total resistance is the sum of individual resistances.
C The total voltage is the same across each component.
D The total resistance is always constant.
In a **series circuit**, the total resistance is the sum of the individual resistances. This means that as more resistors are added, the total resistance increases.
What is the total resistance of two resistors, 3 ohms and 6 ohms, connected in parallel?
A 9 ohms
B 2 ohms
C 1.5 ohms
D 4.5 ohms
The total resistance for resistors in parallel is given by:
**1/R_total = 1/R1 + 1/R2**.
So for 3 ohms and 6 ohms,
**1/R_total = 1/3 + 1/6 = 1/2**,
thus **R_total = 2 ohms**.
What happens to the total impedance in a series RLC circuit at resonance?
A The impedance is minimized.
B The impedance is maximized.
C The current is minimized.
D The impedance is constant.
At **resonance** in a series RLC circuit, the inductive reactance cancels out the capacitive reactance, resulting in a **minimum total impedance** and maximum current.
What does the power factor in an AC circuit measure?
A The ratio of voltage to current.
B The total power used by the circuit.
C The ratio of real power to apparent power.
D The voltage drop across the resistor.
The **power factor** is the ratio of **real power** (the power actually used by the circuit) to **apparent power** (the total power supplied to the circuit). It indicates how efficiently the circuit is using power.
What is the primary purpose of an electrical filter in a circuit?
A To amplify signals.
B To remove unwanted frequencies.
C To increase the voltage.
D To store energy.
**Electrical filters** are designed to allow certain frequencies to pass while blocking others. They are commonly used in signal processing, audio systems, and communication circuits.
What is the main role of a transformer in an electrical circuit?
A To convert AC to DC.
B To change the voltage level.
C To regulate the current.
D To store energy.
A **transformer** is used to change the **voltage level** in an AC circuit, either stepping it up (increasing voltage) or stepping it down (decreasing voltage).
What is the unit of inductance?
A Farad
B Ohm
C Henry
D Volt
The unit of inductance is **henry (H)**. It represents the ability of an inductor to resist changes in current and store energy in a magnetic field.
In a DC circuit, what happens if the power factor is 1?
A The circuit is inefficient.
B The circuit uses all the power effectively.
C The circuit has no power loss.
D The current is zero.
A **power factor of 1** means that all the power supplied to the circuit is being used effectively, with no power lost due to phase differences between current and voltage.
What is the purpose of a feedback loop in an amplifier circuit?
A To regulate the voltage.
B To stabilize the output.
C To increase the frequency of operation.
D To store energy.
**Feedback** in an amplifier circuit is used to **stabilize the output** by reducing fluctuations and ensuring a steady and consistent signal.
What is the main function of a diode in a circuit?
A To amplify the signal.
B To allow current to flow in only one direction.
C To store electrical energy.
D To resist the flow of current.
A **diode** is a semiconductor device that allows **current to flow in one direction only**, making it useful for rectification (converting AC to DC).
What happens in a parallel circuit when more resistors are added?
A The total current decreases.
B The total resistance decreases.
C The total resistance increases.
D The total voltage increases.
In a **parallel circuit**, adding more resistors **decreases the total resistance** because the total resistance is the reciprocal of the sum of reciprocals of the individual resistances.
What is the primary purpose of an energy storage component like a capacitor?
A To increase the current.
B To store electrical energy for later use.
C To resist voltage spikes.
D To convert AC to DC.
A **capacitor** stores electrical energy in an electric field and can release this energy when needed. It is commonly used in smoothing and energy storage applications.
What is an equivalent circuit used for?
A To simplify the analysis of a complex circuit.
B To add more power to a circuit.
C To increase the current in a circuit.
D To filter out unwanted frequencies.
An **equivalent circuit** is a simplified version of a complex circuit that uses basic components like resistors, capacitors, and inductors to model the same behavior for easier analysis.