The unit of electric power is the **watt (W)**. Power is calculated as the product of voltage and current, and one watt is equivalent to one joule of energy per second.
In a series circuit, what happens to the total voltage across the circuit?
A It is divided among the components.
B It is the same across each component.
C It is zero.
D It increases as the current increases.
In a **series circuit**, the total voltage is divided among the components. The sum of the individual voltage drops across all components equals the total supply voltage.
How do you calculate the total resistance in a parallel circuit?
A R_total = R1 + R2 + R3
B 1/R_total = 1/R1 + 1/R2 + 1/R3
C R_total = (R1 * R2) / (R1 + R2)
D R_total = R1 – R2
In a **parallel circuit**, the total resistance is calculated using the reciprocal formula:
**1/R_total = 1/R1 + 1/R2 + 1/R3**. This results in a total resistance lower than the individual resistances.
What does Ohm’s Law relate?
A Power, voltage, and current
B Resistance, voltage, and current
C Current, charge, and time
D Power, energy, and time
**Ohm’s Law** states that the voltage (V) across a resistor is equal to the product of the current (I) through it and the resistance (R). The formula is **V = I * R**.
What is the primary characteristic of an inductive reactance in an AC circuit?
A It opposes changes in voltage.
B It resists the flow of current.
C It allows current to flow easily.
D It stores energy in an electric field.
**Inductive reactance** (XL) opposes changes in current in an AC circuit. It increases with the frequency of the alternating current and stores energy in a magnetic field.
What happens in an AC circuit when the frequency increases?
A The inductive reactance decreases.
B The capacitive reactance increases.
C The total impedance increases in a purely resistive circuit.
D The inductive reactance increases.
**Inductive reactance** (XL) increases with frequency in an AC circuit, as **XL = 2πfL**, where **f** is the frequency and **L** is the inductance.
What is the phase difference between the current and voltage in a purely capacitive AC circuit?
A 0 degrees
B 45 degrees
C 90 degrees (current leads voltage)
D 90 degrees (voltage leads current)
In a **purely capacitive AC circuit**, the current leads the voltage by **90 degrees**. This is due to the phase relationship between current and voltage in capacitors.
What is the primary function of a resistor in an electrical circuit?
A To store electrical energy
B To resist the flow of current
C To amplify signals
D To filter signals
A **resistor** is used to limit or control the flow of electrical current in a circuit. It dissipates electrical energy in the form of heat.
How is the total power in an AC circuit with resistive load calculated?
A P = I² * R
B P = V² / R
C P = V * I * cos(θ)
D P = V * I
The power in an AC circuit is given by the formula **P = V * I * cos(θ)**, where **V** is the voltage, **I** is the current, and **θ** is the phase angle between them. This accounts for the power factor in the circuit.
What is the behavior of a capacitor in a DC circuit after a long time?
A It behaves like a short circuit.
B It behaves like an open circuit.
C It stores infinite energy.
D It dissipates energy.
In a **DC circuit**, after a long time, a capacitor becomes fully charged and behaves like an **open circuit**, meaning no current flows through it.
What is the role of a transformer in an electrical system?
A To convert AC to DC
B To increase or decrease voltage
C To store energy
D To provide constant current
A **transformer** changes the voltage level in an AC circuit. It can either **step up** (increase) or **step down** (decrease) the voltage while keeping the power constant.
What does Kirchhoff’s Voltage Law (KVL) state?
A The sum of all currents entering a junction is zero.
B The sum of the voltage drops around a closed loop is zero.
C The power supplied equals the power consumed.
D The total resistance in a circuit is constant.
**Kirchhoff’s Voltage Law (KVL)** states that the algebraic sum of all voltages in a closed loop equals zero. This law is based on the conservation of energy.
What is the total impedance in a series RLC circuit at resonance?
A The impedance is maximized.
B The impedance is minimized.
C The total current is minimized.
D The total current is maximized.
At **resonance**, the **inductive reactance** cancels out the **capacitive reactance**, resulting in a **minimum total impedance**. This leads to **maximum current** in the circuit.
In a parallel circuit, if one resistor is removed, what happens to the total resistance?
A It increases.
B It decreases.
C It stays the same.
D It becomes zero.
In a **parallel circuit**, removing one resistor increases the total resistance. This is because the total resistance is reduced by adding more resistors, so fewer resistors means higher total resistance.
What is the role of a feedback loop in an amplifier circuit?
A To increase current
B To stabilize and control the output
C To regulate power
D To store energy
A **feedback loop** in an amplifier circuit helps stabilize the output by adjusting the input based on the output signal, ensuring a steady and consistent performance.
What happens in a circuit when the power factor is less than 1?
A The circuit uses all power efficiently.
B Some of the power is wasted as reactive power.
C The current is zero.
D The voltage is equal to current.
A power factor of less than **1** means that not all the power is being used efficiently. The difference between the total power and real power is **reactive power**, which does not perform useful work.
How do you calculate the total current in a series circuit?
A It is the same as the current through any component.
B It is the sum of currents through each component.
C It is the sum of all resistances.
D It is the sum of all voltages.
In a **series circuit**, the **current** is the same through all components. The current does not change across resistors or other components in series.
What is the behavior of the total current in a parallel circuit as more resistors are added?
A It increases.
B It remains the same.
C It decreases.
D It becomes zero.
In a **parallel circuit**, adding more resistors provides additional paths for the current to flow, so the total current in the circuit increases.
What does impedance combine in an AC circuit?
A Resistance and capacitance
B Resistance and reactance
C Current and power
D Voltage and current
**Impedance** is the total opposition to current flow in an AC circuit, combining both **resistance** (R) and **reactance** (which can be inductive or capacitive).
What is the effect of increasing the frequency in a capacitive circuit?
A The capacitive reactance increases.
B The capacitive reactance decreases.
C The total impedance decreases.
D The current decreases.
**Capacitive reactance (XC)** decreases as the frequency increases, as **XC = 1 / (2πfC)**, where **f** is the frequency and **C** is the capacitance.
What happens to the total resistance in a series circuit if the resistance of one resistor increases?
A The total resistance decreases
B The total resistance increases
C The total resistance remains the same
D The current increases
In a series circuit, the total resistance is the sum of the individual resistances. If one resistor’s resistance increases, the total resistance will also increase.
What is the total voltage across the components in a parallel circuit?
A It is divided equally among the components
B It is the same across all components
C It is the sum of individual voltages
D It is zero
In a parallel circuit, the voltage across each component is the same as the source voltage, regardless of the resistance of the components.
What is the formula for calculating the total resistance in a parallel circuit with two resistors, R1 and R2?
A R_total = R1 + R2
B R_total = 1 / (1/R1 + 1/R2)
C R_total = R1 * R2
D R_total = (R1 + R2) / 2
The total resistance in a parallel circuit is calculated using the reciprocal formula: 1/R_total = 1/R1 + 1/R2. This gives a total resistance lower than the smallest individual resistance.
What does Kirchhoff’s Current Law (KCL) state?
A The sum of voltages around a closed loop equals zero
B The sum of currents entering a junction equals the sum of currents leaving the junction
C The current in a circuit is constant
D The voltage across resistors is constant
Kirchhoff’s Current Law (KCL) states that the total current entering a junction (or node) in a circuit is equal to the total current leaving that junction, based on the principle of conservation of charge.
What happens to the current in a series circuit if the total resistance is increased?
A The current decreases
B The current increases
C The current stays the same
D The current becomes zero
According to Ohm’s Law (V = I * R), if the total resistance in a series circuit increases, the current will decrease, assuming the voltage remains constant.
What is the relationship between current and voltage in a resistive circuit according to Ohm’s Law?
A Voltage is inversely proportional to current
B Voltage is directly proportional to current
C Voltage is constant
D Current is constant
According to Ohm’s Law, the voltage across a resistor is directly proportional to the current flowing through it, with resistance as the proportionality constant. The formula is **V = I * R**.
How is the total power in an electrical circuit calculated?
A Power = Voltage × Resistance
B Power = Current × Voltage
C Power = Voltage / Current
D Power = Current × Resistance
The total power dissipated in an electrical circuit is given by the formula **P = I * V**, where **I** is the current and **V** is the voltage.
What is the main function of an inductor in an AC circuit?
A To store energy in an electric field
B To store energy in a magnetic field
C To resist changes in voltage
D To convert AC to DC
An **inductor** stores energy in the form of a magnetic field when current flows through it. It resists changes in current and opposes voltage fluctuations.
What is the unit of reactance in an AC circuit?
A Volt
B Ampere
C Ohm
D Henry
The unit of **reactance** (whether inductive or capacitive) is the **ohm (Ω)**, which is the same as resistance. Reactance refers to the opposition to current flow in AC circuits caused by inductance or capacitance.
What is the primary purpose of a capacitor in an electrical circuit?
A To increase current flow
B To store electrical energy in an electric field
C To filter out noise
D To store electrical energy in a magnetic field
A **capacitor** stores electrical energy in an electric field between two conductive plates. It is commonly used to store and release energy and to filter or smooth signals.
What happens to the current in a parallel circuit when more resistors are added?
A The current decreases
B The current increases
C The current stays the same
D The current becomes zero
In a **parallel circuit**, adding more resistors provides additional paths for current to flow, which increases the total current supplied by the source.
What is the unit of inductance?
A Watt
B Volt
C Henry
D Ampere
The unit of **inductance** is the **henry (H)**, which represents the ability of an inductor to oppose changes in current in an AC circuit.
What is the main function of a transformer in an electrical system?
A To store electrical energy
B To increase or decrease voltage
C To control current flow
D To filter out noise
A **transformer** is used to change the voltage level in an AC circuit. It can either **step up** (increase) or **step down** (decrease) the voltage depending on the turns ratio between its coils.
What happens in a DC circuit when the power factor is 1?
A The circuit is inefficient
B The circuit uses all power effectively
C The current is zero
D The voltage is equal to current
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 unit of reactance in an AC circuit?
A Watt
B Ohm
C Volt
D Ampere
The unit of **reactance** (whether inductive or capacitive) is the **ohm (Ω)**, which is the same as resistance. Reactance refers to the opposition to current flow in AC circuits caused by inductance or capacitance.
What is the main function of a feedback mechanism in an electrical circuit?
A To store energy
B To stabilize the circuit’s performance
C To increase power
D To decrease current flow
**Feedback mechanisms** are used to adjust the output of a circuit based on its input, helping to stabilize performance, reduce fluctuations, and improve overall control.
What happens to the voltage in a series circuit if the total resistance increases?
A The voltage decreases
B The voltage increases
C The voltage remains the same
D The voltage becomes zero
In a **series circuit**, if the total resistance increases, the voltage is divided across the resistors, resulting in a drop in the voltage available to each component.
What is the phase difference between current and voltage in a purely inductive AC circuit?
A 0 degrees
B 45 degrees
C 90 degrees (current lags voltage)
D 180 degrees
In a **purely inductive AC circuit**, the **current lags the voltage by 90 degrees**. This phase shift occurs due to the inductive reactance, which resists changes in current.
What happens in an electrical circuit when the power factor is less than 1?
A The circuit uses all power efficiently
B Some of the power is wasted as reactive power
C The current is zero
D The voltage is equal to current
A power factor less than **1** means that some of the power is being lost as reactive power, which does not perform useful work.
What is the primary purpose of a diode in an electrical circuit?
A To amplify the signal
B To allow current to flow in only one direction
C To resist current flow
D To store electrical energy
A **diode** allows current to flow only in one direction, making it useful for converting alternating current (AC) to direct current (DC) in rectification circuits.
What is transient analysis used to study in an electrical circuit?
A Behavior at steady state
B Behavior after a sudden change in conditions
C Behavior of DC circuits
D Behavior of passive components only
Transient analysis is used to study how electrical circuits respond to sudden changes, such as when a switch is turned on or off, or there are sudden voltage or current variations.
In steady-state analysis of an AC circuit, what happens to the current and voltage over time?
A They both increase
B They both become constant
C They oscillate
D They become zero
In steady-state analysis, after transient effects have settled, the current and voltage reach a constant value, and the circuit exhibits periodic behavior with stable voltage and current waveforms.
What does a phasor represent in AC circuit analysis?
A A sinusoidal waveform in the time domain
B A complex number that represents a sinusoidal waveform in the frequency domain
C A capacitor in a circuit
D A resistor with varying resistance
A phasor is a complex number that represents the amplitude and phase of a sinusoidal waveform, which simplifies AC circuit analysis by converting sinusoidal signals into complex numbers in the frequency domain.
What happens to the impedance in a circuit with both resistive and inductive components?
A It is purely resistive
B It is purely inductive
C It combines both resistance and reactance
D It becomes zero
In a circuit with both resistive and inductive components, the total impedance is the combination of both the resistance (R) and inductive reactance (XL). The impedance thus includes both resistive and reactive elements.
What does admittance in an AC circuit represent?
A The total resistance of the circuit
B The reciprocal of impedance
C The total current in the circuit
D The energy stored in the circuit
**Admittance** is the reciprocal of **impedance** and represents how easily current flows through a circuit. It is measured in siemens (S), and a higher admittance means lower opposition to current flow.
What is the formula for calculating the impedance of a series RLC circuit?
A Z = R + XL + XC
B Z = R + j(XL – XC)
C Z = √(R² + (XL – XC)²)
D Z = R + jXL + jXC
The **impedance** of a series **RLC circuit** is given by the formula **Z = R + j(XL – XC)**, where **R** is the resistance, **XL** is the inductive reactance, and **XC** is the capacitive reactance. The imaginary unit **j** represents the phase difference between the components.
What is the effect of resonance in an RLC circuit?
A The impedance is maximized
B The inductive and capacitive reactances cancel each other out
C The current is minimized
D The voltage becomes zero
At **resonance** in an **RLC circuit**, the **inductive reactance** cancels out the **capacitive reactance**, resulting in minimum impedance and maximum current flow.
What happens to the impedance in a purely capacitive AC circuit as the frequency increases?
A It increases
B It decreases
C It remains constant
D It becomes infinite
In a **purely capacitive AC circuit**, the **capacitive reactance (XC)** decreases as the frequency increases because **XC = 1 / (2πfC)**, where **f** is the frequency and **C** is the capacitance.
What does the term “reactance” refer to in an AC circuit?
A The opposition to current due to resistance
B The opposition to current due to inductance or capacitance
C The current flowing through the circuit
D The voltage across components
**Reactance** refers to the opposition to current flow in an AC circuit caused by inductance (**XL**) or capacitance (**XC**). Unlike resistance, reactance depends on the frequency of the AC signal.
What does the **power factor** in an AC circuit indicate?
A The efficiency of energy storage
B The ratio of real power to apparent power
C The frequency of the circuit
D The total impedance
**Power factor** is the ratio of real power (useful power) to apparent power (total power supplied). A power factor of 1 indicates maximum efficiency where all power is used effectively.