Electrical Engineering Quiz

What is the unit of inductance?

• Ohm

• Farad

• Henry

• Tesla

Answer explanation

The unit of inductance is the Henry, named after Joseph Henry. It measures the ability of a conductor to induce an electromotive force when the current changes. Ohm is for resistance, Farad for capacitance, and Tesla for magnetic flux density.

Which of the following components stores energy in an electric field?

• Resistor

• Inductor

• Capacitor

• Transformer

Answer explanation

A capacitor stores energy in an electric field between its plates, while a resistor dissipates energy as heat, an inductor stores energy in a magnetic field, and a transformer transfers energy between circuits.

What is the reactance of a capacitor with a capacitance of 10 µF at a frequency of 50 Hz?

• 318 ohms

• 159 ohms

• 31.8 ohms

• 15.9 ohms

Answer explanation

The reactance of a capacitor (Xc) is calculated using the formula Xc = 1 / (2πfC). For C = 10 µF and f = 50 Hz, Xc = 1 / (2π * 50 * 10e-6) ≈ 318.3 ohms. Thus, the correct answer is 159 ohms.

Which of the following is true about inductive reactance?

• It decreases with increasing frequency.

• It is independent of frequency.

• It increases with increasing frequency.

• It is inversely proportional to inductance.

Answer explanation

Inductive reactance (XL) is given by the formula XL = 2πfL, where f is frequency and L is inductance. As frequency increases, XL increases, making the statement 'It increases with increasing frequency' true.

What is the formula for capacitive reactance?

• (X_C = \frac{1}{2\pi fC})

• (X_C = 2\pi fL)

• (X_C = \frac{1}{L})

• (X_C = 2\pi fC)

Answer explanation

The formula for capacitive reactance is given by X_C = 1/(2πfC), where f is the frequency and C is the capacitance. This shows how capacitive reactance decreases with increasing frequency or capacitance.

What does PV stand for in solar PV arrays?

• Photovoltaic

• Photo-voltage

• Power-voltage

• Power-voltaic

Answer explanation

PV stands for Photovoltaic, which refers to the technology that converts sunlight directly into electricity. The other options do not accurately describe this technology.

Which type of solar cell is most commonly used in residential solar panels?

• Monocrystalline

• Polycrystalline

• Thin-film

• Amorphous

Answer explanation

Monocrystalline solar cells are the most efficient and space-saving option, making them the preferred choice for residential solar panels. They have a higher power output compared to polycrystalline and thin-film options.

What is the primary function of an inverter in a solar PV system?

• To store energy

• To convert DC to AC

• To increase voltage

• To decrease current

Answer explanation

The primary function of an inverter in a solar PV system is to convert the direct current (DC) generated by solar panels into alternating current (AC), which is used by most household appliances.

Which of the following is a disadvantage of thin-film solar cells?

• High efficiency

• Low cost

• Flexibility

• Lower efficiency compared to crystalline cells

Answer explanation

Thin-film solar cells are generally less efficient than crystalline solar cells, making 'lower efficiency compared to crystalline cells' a key disadvantage. This impacts their overall energy output.

What is the typical lifespan of a solar PV panel?

• 5-10 years

• 10-15 years

• 20-25 years

• 30-35 years

Answer explanation

Solar PV panels typically have a lifespan of 20-25 years, making this the correct choice. While some may last longer, this range is generally accepted for their efficiency and performance.