# FREE GROL General Radiotelephone Questions and Answers

#### What formula would determine the inductive reactance of a coil if frequency and coil inductance are known?

Explanation:

The formula to determine the inductive reactance (XL) of a coil when frequency (f) and coil inductance (L) are known is XL = 2πf L. This formula is derived from the relationship between inductance, frequency, and inductive reactance in an AC circuit.

#### Which of the following groups is correct for listing common materials in order of descending conductivity?

Explanation:

In terms of electrical conductivity, materials are typically ranked in descending order as follows: silver, copper, aluminum, iron, and lead. Silver has the highest electrical conductivity among common materials, followed by copper, aluminum, iron, and lead. This ranking reflects the ability of these materials to conduct electrical current efficiently.

#### The second harmonic of a 380 kHz frequency is:

Explanation:

The second harmonic of a frequency is double the original frequency. Therefore, the second harmonic of a 380 kHz frequency would be 760 kHz.

#### Which of the following Ohm Law formulas is incorrect?

Explanation:

Ohm's Law states that the current (I) flowing through a conductor is directly proportional to the voltage (E) applied across it and inversely proportional to the resistance (R) of the conductor. Therefore, the correct formula is I = E / R, not I = R / E.

#### Which of the 4 groups of metals listed below are the best low-resistance conductors?

Explanation:

Gold, silver, and copper are known for their excellent electrical conductivity and are commonly used as low-resistance conductors in various electrical and electronic applications. Their high conductivity allows for efficient transmission of electrical signals with minimal loss.

#### How does the input impedance of a field-effect transistor compare with that of a bipolar transistor?

Explanation:

Field-effect transistors (FETs) typically have high input impedance, meaning they present a high resistance to the input signal, while bipolar transistors have lower input impedance. This difference arises from the distinct mechanisms of operation between the two types of transistors.

#### At 150 degrees, what is the amplitude of a sine wave having a peak value of 5 volts?

Explanation:

The amplitude of a sine wave refers to half of the peak-to-peak voltage. Since the peak value is 5 volts, the peak-to-peak voltage is 10 volts. At 150 degrees, the sine wave has reached halfway between its peak and trough, which corresponds to half of the peak-to-peak voltage. Therefore, the amplitude at 150 degrees is +2.5 volts.

#### Which of these will be most useful for insulation at UHF frequencies?

Explanation:

At UHF frequencies (Ultra-High Frequencies), which typically range from 300 MHz to 3 GHz, mica is the most useful material for insulation. Mica has low loss and high stability characteristics at these frequencies, making it suitable for use in high-frequency circuits where minimal signal loss and stability are crucial.

#### In a circuit where the AC voltage and current are out of phase, how can the true power be determined?

Explanation:

In a circuit where the AC voltage and current are out of phase, the true power (in watts) can be determined by multiplying the apparent power (in volt-amperes) by the power factor. The power factor represents the cosine of the phase angle between the voltage and current waveforms. This calculation accounts for the phase difference between voltage and current, providing an accurate measure of the power dissipated in the circuit.

#### What is the description of a square wave?

Explanation:

A square wave is a waveform characterized by abrupt changes between two voltage levels, typically high and low, and it remains at each level for equal durations of time. This results in a waveform that resembles a series of square-shaped pulses.

#### Permeability is defined as:

Explanation:

Permeability is defined as the ratio of the magnetic flux density (B) in a substance to the magnetizing force (H) that produces it. It quantifies how easily a material can be magnetized by an external magnetic field.