1.
Proper biasing in an amplifier circuit
Correct Answer
C. Can be obtained using a voltage divider network
Explanation
Proper biasing in an amplifier circuit can be obtained using a voltage divider network. Biasing is the process of setting the DC operating point of the amplifier to ensure that it operates within its linear range. A voltage divider network is commonly used to provide a stable and appropriate bias voltage to the amplifier circuit. It divides the input voltage into smaller fractions, allowing the desired bias voltage to be applied to the amplifier. This helps in achieving the desired operating conditions and ensures proper amplification without distortion or damage to the circuit components.
2.
A transistor can be protected from needless overheating by
Correct Answer
A. A current-limiting resistor
Explanation
A current-limiting resistor can protect a transistor from overheating by limiting the amount of current flowing through it. When the current flowing through the transistor exceeds its maximum rating, it can cause overheating and damage the device. By adding a current-limiting resistor in series with the transistor, the resistor will restrict the amount of current that can flow through the transistor, preventing it from overheating. This ensures that the transistor operates within its safe operating limits and prolongs its lifespan.
3.
A bleeder resistor
Correct Answer
A. Is connected across the capacitor in a power supply
Explanation
A bleeder resistor is connected across the capacitor in a power supply to prevent the capacitor from retaining a dangerous charge when the power supply is turned off. This resistor allows the capacitor to discharge slowly and safely, ensuring that the transistor or amplifier connected to the power supply does not draw too much current or get damaged. By discharging the capacitor, the bleeder resistor also helps optimize the efficiency of the amplifier by preventing any residual charge from affecting its performance.
4.
Carbon-composition resistors
Correct Answer
C. Have essentially no capacitance or inductance
Explanation
Carbon-composition resistors have essentially no capacitance or inductance. This means that they do not store electrical charge or create a magnetic field when a voltage is applied. This property makes them ideal for applications where precise resistance values are required without any unwanted effects from capacitance or inductance. It ensures that the resistor will accurately control the flow of current without introducing any additional impedance or distortion to the circuit.
5.
A logical place for a wirewound resistor is
Correct Answer
D. In a high-power dc circuit
Explanation
A wirewound resistor is commonly used in high-power DC circuits because it can handle high levels of current and dissipate large amounts of power without overheating. Wirewound resistors are designed with a coil of wire wrapped around a ceramic or fiberglass core, which provides high resistance values and low inductance. This makes them suitable for applications where high power dissipation is required, such as in power supplies, motor control circuits, or high-power audio amplifiers. In contrast, radio-frequency amplifiers typically require resistors with low inductance to avoid interfering with the signal, so a wirewound resistor would not be the best choice in that scenario.
6.
A metal-film resistor
Correct Answer
B. Does not have much inductance
Explanation
A metal-film resistor does not have much inductance because it is made using a carbon-based paste. The carbon-based paste used in the resistor helps to reduce inductance, which is the property of a component that resists changes in current flow. Therefore, the metal-film resistor is designed to minimize inductance and provide a more accurate resistance value without the interference of inductive effects.
7.
What type of resistor, or combination of resistors, would you use as the meter-sensitivity
control in a test instrument, when continuous adjustment is desired?
Correct Answer
B. A linear-taper potentiometer
Explanation
A linear-taper potentiometer would be used as the meter-sensitivity control in a test instrument when continuous adjustment is desired. A potentiometer is a variable resistor that allows for precise control over the resistance value. A linear-taper potentiometer has a uniform change in resistance per unit of rotation, making it suitable for continuous adjustment. This allows the user to finely tune the sensitivity of the meter in the test instrument to their desired level. Switchable, fixed resistors would not provide continuous adjustment, while an audio-taper potentiometer and a wirewound resistor may not provide the desired level of precision.
8.
What type of resistor, or combination of resistors, would you use as the volume control in astereo compact-disc (CD) player?
Correct Answer
C. An audio-taper potentiometer
Explanation
An audio-taper potentiometer would be used as the volume control in a stereo CD player because it provides a logarithmic response to changes in resistance. This means that the volume changes more gradually at lower levels and more rapidly at higher levels, which matches the way our ears perceive sound. Switchable fixed resistors would not allow for smooth volume adjustments, and a linear-taper potentiometer would not accurately reflect the logarithmic response of our ears. A wirewound resistor is not typically used as a volume control in audio applications.
9.
If a sound triples in actual power level, approximately what is this, expressed in decibels?
Correct Answer
B. +5 dB
Explanation
When a sound triples in actual power level, it means that the power has increased by a factor of 3. In decibels, a doubling of power corresponds to an increase of approximately 3 dB. Since the power has tripled, the increase in decibels would be slightly more than 3 dB, but not as much as 6 dB. Therefore, the closest option is +5 dB, which is a reasonable approximation for a tripling of power level.
10.
Suppose a sound changes in volume by −13 dB. If the original sound power is 1.0 W, what is
the final sound power?
Correct Answer
C. 50 mW
Explanation
The given question provides the information that the sound changes in volume by -13 dB and the original sound power is 1.0 W. To find the final sound power, we need to use the formula: final power = original power * 10^(change in dB/10). Plugging in the values, we get the final power = 1.0 W * 10^(-13/10) = 1.0 W * 0.0501 = 0.0501 W = 50 mW. Therefore, the correct answer is 50 mW.
11.
The sound from a portable radio is at a level of 50 dB. How many times the threshold ofhearing is this, in terms of actual sound power?
Correct Answer
D. 100,000
Explanation
The threshold of hearing is the minimum sound level that can be detected by the human ear. It is generally considered to be around 0 dB. In this question, the sound from the portable radio is measured at 50 dB, which is 50 decibels above the threshold of hearing. Decibels are a logarithmic scale, so each increase of 10 dB represents a tenfold increase in sound power. Therefore, 50 dB is 10^5 (100,000) times the threshold of hearing in terms of actual sound power.
12.
An advantage of a rheostat over a potentiometer is the fact that
Correct Answer
C. A rheostat can handle more current
Explanation
A rheostat can handle more current compared to a potentiometer. This means that it can handle a higher amount of electric current flowing through it without getting damaged or overheating. This advantage makes the rheostat suitable for applications where a higher current capacity is required, such as controlling the brightness of high-power lamps or regulating the speed of motors.
13.
A resistor is specified as having a value of 68 Ω, but is measured with an ohmmeter as 63 Ω.The value is off by which of the following percentages?
Correct Answer
A. 7.4%
Explanation
The value of the resistor is off by 7.4%. This can be calculated by finding the difference between the specified value (68 Ω) and the measured value (63 Ω), which is 5 Ω. Then, divide this difference by the specified value and multiply by 100 to get the percentage difference. In this case, (5 Ω / 68 Ω) * 100 = 7.4%. Therefore, the correct answer is 7.4%.
14.
Suppose a resistor is rated at 3.3 kΩ 5%. This means it can be expected to have a value
between
Correct Answer
C. 3135 Ω and 3465 Ω
Explanation
The given resistor is rated at 3.3 kΩ with a tolerance of 5%. The tolerance indicates the range within which the actual value of the resistor can vary. In this case, the tolerance of 5% means that the actual value of the resistor can be 5% higher or lower than the rated value. To find the range, we calculate 5% of 3.3 kΩ, which is 0.165 kΩ. Subtracting this value from 3.3 kΩ gives us 3.135 kΩ, and adding it to 3.3 kΩ gives us 3.465 kΩ. Converting these values to ohms, we get 3135 Ω and 3465 Ω, which represents the expected range of the resistor's value.
15.
A package of resistors is rated at 56 Ω 10%. You test them with an ohmmeter. Which ofthe following values indicates a reject?
Correct Answer
A. 50.0 Ω
Explanation
The package of resistors is rated at 56 Ω ±10%. This means that the acceptable range for the resistors is between 50.4 Ω and 61.6 Ω. Since the value of 50.0 Ω falls below this range, it indicates a reject.
16.
A resistor has a value of 680 Ω, and you expect that it will have to draw 1 mA maximumcontinuous current in a circuit you’re building. What power rating is good for this application,but not needlessly high?
Correct Answer
A. 1⁄4 W
Explanation
A resistor with a value of 680 Ω and a maximum continuous current of 1 mA can be calculated using the formula P = I^2 * R, where P is the power, I is the current, and R is the resistance. Plugging in the values, we get P = (0.001 A)^2 * 680 Ω = 0.00068 W. Therefore, a power rating of 1⁄4 W is good for this application as it provides a sufficient margin for the expected current without being needlessly high.
17.
Suppose a 1-kΩ resistor will dissipate 1.05 W, and you have a good supply of 1-W resistors of
various ohmic values. If there’s room for 20 percent resistance error, the cheapest solution is to use
Correct Answer
B. A pair of 2.2-kΩ, 1-W resistors in parallel
Explanation
The cheapest solution is to use a pair of 2.2-kΩ, 1-W resistors in parallel because when resistors are connected in parallel, their total resistance is calculated as the reciprocal of the sum of the reciprocals of the individual resistances. In this case, two 2.2-kΩ resistors in parallel would yield a total resistance of 1.1 kΩ, which is within the 20 percent resistance error limit. Additionally, using two 1-W resistors in parallel would provide a power dissipation capacity of 2 W, which is more than the 1.05 W required.
18.
Suppose a carbon-composition resistor has the following colored bands on it: red, red, red,
gold. This indicates a resistance of
Correct Answer
C. 2.2 kΩ
Explanation
The colored bands on a carbon-composition resistor indicate the resistance value. In this case, the bands are red, red, red, and gold. The first three red bands represent the digits 2, 2, and 2, respectively. The gold band represents the multiplier 100, which means the resistance value should be multiplied by 100. Therefore, the resistance is calculated as 2.2 * 1000 = 2200 ohms or 2.2 kΩ.
19.
The actual resistance of the component described in the previous question can be expected tovary above or below the specified ohmic value by up to what amount?
Correct Answer
B. 110 Ω
Explanation
The actual resistance of the component described in the previous question can be expected to vary above or below the specified ohmic value by up to 110 Ω.
20.
Suppose a carbon-composition resistor has the following colored bands on it: gray, red,
yellow. This unit can be expected to have a value within approximately what range?
Correct Answer
A. 660 kΩ to 980 kΩ
Explanation
The colored bands on a carbon-composition resistor indicate its resistance value. In this case, the gray band represents the first digit, which is 6. The red band represents the second digit, which is 6. The yellow band represents the multiplier, which is 10^3 or 1000. Therefore, the value of the resistor can be calculated as 66 * 1000 = 66000 ohms or 66 kΩ. However, since carbon-composition resistors have a tolerance of around 20%, the actual value can vary within a certain range. Therefore, the expected range for this resistor is approximately 660 kΩ to 980 kΩ.