Electrical Science - Impedance

Multiple Choice

What is the phase angle between the voltages of the inductor and capacitor in a RLC series circuit?

• zero

• 90°

• 180°

• 270°

Multiple Choice

What is the formula for calculating impedance, Z?

• Z = R + X

• Z = R - X

• Z = √(R² + X²)

• Z = R * X

Multiple Choice

What is the formula for the voltage across the coil in an AC circuit?

• V_L = I × X_L

• V_R = I × R

• V_S = I × Z

• V = I × R + I × X_L

Multiple Choice

What is the formula for calculating impedance (Z) in a circuit containing resistance (R) and inductive reactance (X_L)?

• Z = R + X_L

• Z = R - X_L

• Z = R * X_L

• Z = √(R² + X_L²)

Multiple Choice

A basic unit of reactance is

• whatt

• ohm

• XL

• resistive opposition

Multiple Choice

A basic unit of reactance and inductance is

• whatt

• ohm

• XL

• resistive opposition

Multiple Choice

What is the formula for calculating impedance (Z) in a circuit containing resistance (R) and reactance (Xc)?

• Z = R + Xc

• Z = R - Xc

• Z = √(R² + Xc²)

• Z = R * Xc

Multiple Choice

What is the formula for calculating impedance (Z) in a circuit containing resistance (R), inductive reactance (X_L), and capacitive reactance (X_C)?

• Z = √(R² + (X_L - X_C)²)

• Z = R + X_L + X_C

• Z = R - (X_L + X_C)

• Z = (X_L + X_C) / R

Multiple Choice

What can phasor diagrams resolve in a series circuit?

• Currents

• Voltages

• Resistances

• Inductances

Multiple Choice

What is the relationship between the voltage and current in a phasor diagram for R and XL in series?

• Voltage is constant

• Current varies

• Voltage varies

• Both voltage and current are constant

Multiple Choice

What is the formula for calculating the power factor in an AC circuit?

• pf = R/Z

• pf = V_R/V_S

• pf = cosφ

• pf = R*Z

Multiple Select

If the voltages across VR and VL are 70V and 120V respectively, calculate: a. the supply voltage b. phase angle of the circuit c. sketch the phasor diagram.

• Supply voltage

• Phase angle

• Phasor diagram

• None of the above

Multiple Choice

Calculate the value of Vs using the formula Vs = √(VR² + VL²). What is the value of Vs?

• 70 volts

• 120 volts

• 138.92 volts

• 19300 volts

Multiple Choice

What is the value of V_L when V_S is 230 volts and V_R is 115 volts?

• 115 volts

• 199 volts

• 230 volts

• 39675 volts

Multiple Choice

What is the value of cosΦ in the given example?

• 0.5

• 0.6

• 0.7

• 0.8

Multiple Select

A circuit supplied at 230V 50Hz consists of a resistor of 25Ω and an inductor of 0.05 connected in series. Calculate: a. the impedance of the circuit b. the phase angle of the current c. the current flowing in the circuit d. the voltage across each component e. the power consumed by the circuit.

• Impedance

• Phase angle

• Current

• Voltage

Multiple Choice

What is the phase angle (Φ) if cos(Φ) = R/Z, given R = 25 Ω and Z = 29.5 Ω?

• 0.85 lagging

• 31.1° lagging

• 25 Ω

• 15.7 Ω

Multiple Choice

What is the impedance (Z) calculated using the formula Z = √(R² + X_L²) if R = 25 Ω and X_L = 15.7 Ω?

• 29.5 Ω

• 15.7 Ω

• 871.5 Ω

• 25 Ω

Multiple Choice

Calculate the inductive reactance (X_L) using the formula X_L = 2πfL, where f = 50 Hz and L = 0.05 H. What is the value of X_L?

• 15.7 Ω

• 29.5 Ω

• 25 Ω

• 871.5 Ω

Multiple Choice

What is the formula for calculating the current (I) in an AC circuit?

• I = V/Z

• I = V*Z

• I = V+Z

• I = V-Z

Multiple Choice

What is the relationship between the capacitor voltage and the current in the capacitor according to ac theory?

• The capacitor voltage leads the current by 90°

• The capacitor voltage lags the current by 90°

• The current and voltage are in phase

• The current lags the voltage by 90°

Multiple Choice

In the phasor diagram, what is the relationship between voltage (VR) and current (IRef) for the resistor?

• VR = I.R

• VR = I.Xc

• VR = I.Z

• VR = I.C

Multiple Choice

What is the formula for the power factor in terms of resistance and impedance?

• pf = VR/VS

• pf = VS/VR

• pf = R/Z

• pf = Z/R

Multiple Choice

What is the unit of electrical power?

• Joule

• Watt

• Ohm

• Volt

Multiple Choice

Which of the following is a correct representation of electrical power?

• $$P = \frac{V}{I}$$

• $$P = VI$$

• $$P = \frac{I}{V}$$

• $$P = V + I$$

Multiple Choice

Calculate the electrical power if the current is 3 A and the voltage is 12 V.

• 36 W

• 4 W

• 15 W

• 9 W

Multiple Choice

What is the value of Vs in the given example?

• 100 volts

• 207 volts

• 230 volts

• 52849 volts

Multiple Choice

Which of the following is a characteristic of alternating current (AC) but not direct current (DC)?

• Flows in one direction

• Has a constant voltage

• Can be easily transformed to different voltages

• Used in batteries

Multiple Choice

What is the value of V_C calculated from the equation V_C = √(V_S² - V_R²) given that V_S = 230 volts and V_R = 200 volts?

• 114 volts

• 200 volts

• 230 volts

• 129 volts

Multiple Choice

In the given AC theory diagram, what is the value of the voltage across the capacitor (Vc)?

• 200V

• 114V

• 230V

• 30°

Multiple Select

A 31.9μF capacitor is connected in series with a 60Ω resistor across a 230V 50Hz supply. Calculate: a. the impedance of the circuit b. the phase angle of the current c. the current flowing in the circuit d. the voltage across each component e. the power consumed by the circuit.

• impedance of the circuit

• phase angle of the current

• current flowing in the circuit

• voltage across each component