1.
The property of inductance offers opposition to which of the following quantities?
Correct Answer
C. Changes in current
Explanation
Inductance offers opposition to changes in current. This is because inductors store energy in a magnetic field, and any change in current through the inductor induces a change in the magnetic field. The induced magnetic field then opposes the change in current, resulting in opposition to changes in current.
2.
What is the symbol for inductance?
Correct Answer
A. L
Explanation
The symbol for inductance is represented by the letter "L" in electrical circuits. Inductance is a property of an electrical circuit that opposes any changes in the current flowing through it. It is measured in henries (H). The other options, XL and IND, are not commonly used symbols for inductance.
3.
What is the unit of measurement for inductance?
Correct Answer
D. Henry
Explanation
The unit of measurement for inductance is Henry. Inductance is a property of an electrical circuit that opposes changes in current. It is measured in Henry, named after American scientist Joseph Henry, who made significant contributions to the understanding of electromagnetism.
4.
If 9 volts are induced in a conductor when the current changes by 4.5 amperes in one second, what is the total inductance of the circuit?
Correct Answer
B. 2.0 henries
Explanation
When a current changes in a circuit, it induces a voltage in the conductor according to Faraday's law of electromagnetic induction. The induced voltage is directly proportional to the rate of change of current and the inductance of the circuit. In this case, the current changes by 4.5 amperes in one second and induces a voltage of 9 volts. By rearranging the formula V = L * (dI/dt), where V is the induced voltage, L is the inductance, and (dI/dt) is the rate of change of current, we can solve for L. Plugging in the given values, we find that the inductance of the circuit is 2.0 henries.
5.
What physical property is similar to inductance?
Correct Answer
D. Inertia
Explanation
Inertia is the physical property that is similar to inductance. Inertia is the resistance of an object to changes in its motion, while inductance is the property of an electrical circuit that opposes changes in current flow. Both inertia and inductance involve a resistance or opposition to change, making them similar physical properties.
6.
The difference in potential across a resistor, created by current through the resistor is an example of which of the following forces?
Correct Answer
D. Electromotive
Explanation
The difference in potential across a resistor, created by current through the resistor, is an example of electromotive force. Electromotive force, also known as voltage, is the driving force that pushes the electric charges through a circuit. In this case, the current flowing through the resistor creates a potential difference, or voltage, across it. This voltage is the electromotive force that causes the charges to move through the resistor.
7.
When a magnetic field moves through a stationary conductor, the electrons in orbit are affected in what manner?
Correct Answer
A. They are dislodged from orbit
Explanation
When a magnetic field moves through a stationary conductor, the magnetic field induces a current in the conductor. This current creates a force on the electrons in the conductor, causing them to move. As a result, the electrons are dislodged from their original orbits around the nucleus of the atoms in the conductor. This phenomenon is known as the Hall effect, and it is the basis for many practical applications such as magnetic sensors and current measurements.
8.
When electrons are moved in a conductor by a magnetic field, a force known by which of the following terms is created?
Correct Answer
B. Electromotive
Explanation
When electrons are moved in a conductor by a magnetic field, a force known as electromotive force (EMF) is created. EMF is the force that pushes the electrons through the conductor and causes them to flow in a certain direction. It is responsible for the generation of electric current in a circuit. Voltage and potential difference are both terms used to describe the magnitude of the EMF. Therefore, the correct answer is "Electromotive".
9.
Self-induced emf is also known as what force?
Correct Answer
D. Counter electromotive force
Explanation
Self-induced emf refers to the phenomenon where a changing magnetic field induces an opposing voltage in a conductor, according to Faraday's law of electromagnetic induction. This induced voltage is known as counter electromotive force (CEMF), which opposes the change in current flow. Therefore, the correct answer is CEMF.
10.
According to Lenz’s Law, the induced emf produced by a change in current in an inductive circuit tends to have what effect on the current?
Correct Answer
C. It opposes either a rise or a fall in current
Explanation
According to Lenz's Law, the induced emf produced by a change in current in an inductive circuit tends to oppose the change in current. This means that if there is a rise in current, the induced emf will try to reduce the current. Similarly, if there is a fall in current, the induced emf will try to increase the current. Therefore, the correct answer is "It opposes either a rise or a fall in current."
11.
The direction of the induced voltage in an inductor may be found by the application of which of the following rules?
Correct Answer
B. The left-hand rule for generators
Explanation
The left-hand rule for generators can be used to determine the direction of the induced voltage in an inductor. This rule states that if the thumb, index finger, and middle finger of the left hand are extended perpendicular to each other, with the index finger representing the direction of the magnetic field and the middle finger representing the direction of the current, then the thumb will indicate the direction of the induced voltage.
12.
The left-hand rule for generators states that the thumb of the left-hand points in the direction of motion of the:
Correct Answer
A. Conductor
Explanation
The left-hand rule for generators states that the thumb of the left hand points in the direction of motion of the conductor. This rule is used to determine the direction of the induced current in a generator. When a conductor moves through a magnetic field, it experiences a force that causes the electrons in the conductor to move, creating an induced current. By using the left-hand rule, we can determine the direction of this current based on the motion of the conductor.
13.
When source voltage is removed from a current-carrying conductor, a voltage will be induced in the conductor by which of the following actions?
Correct Answer
C. The reversal of current
Explanation
When the source voltage is removed from a current-carrying conductor, a voltage will be induced in the conductor by the reversal of current. This is because when the source voltage is removed, the magnetic field around the conductor collapses. This collapsing magnetic field induces a voltage in the conductor, causing the current to reverse its direction. This phenomenon is known as self-induction or back EMF (electromotive force). The reversal of current helps to maintain the flow of current in the conductor even after the source voltage is removed.
14.
The property of inductance is present in which of the following electrical circuits?
Correct Answer
A. An ac circuit
Explanation
The property of inductance is present in an AC circuit. Inductance is the property of an electrical circuit that opposes changes in current flow. It is caused by the presence of an inductor, which is a coil of wire that stores energy in its magnetic field. In an AC circuit, the current continuously changes direction, causing the magnetic field in the inductor to constantly expand and collapse. This results in the generation of an induced voltage that opposes the change in current, exhibiting the property of inductance. In contrast, in a DC circuit or a resistive circuit, where the current is constant or there is no inductor present, the property of inductance is not applicable.
15.
How are inductors classified?
Correct Answer
A. By core type
Explanation
Inductors are classified by core type, which refers to the material used for the core of the inductor. Different core materials have different magnetic properties, which affect the inductor's performance. The most common core types are air core, iron core, ferrite core, and toroidal core. Each core type has its own advantages and disadvantages, making it suitable for different applications. By classifying inductors based on core type, it becomes easier to select the right inductor for a specific circuit or system.
16.
Normally, most coils have cores composed of either air or:
Correct Answer
C. Soft iron
Explanation
Soft iron is commonly used as a core material in coils because it has high magnetic permeability, which allows it to easily magnetize and demagnetize. This property makes soft iron ideal for enhancing the magnetic field produced by the coil. Additionally, soft iron has low electrical conductivity, which reduces eddy currents and energy losses in the core. This makes soft iron an efficient and effective choice for core material in coils.
17.
The hollow form of nonmagnetic material found in the center of an aircore coil has what purpose?
Correct Answer
D. To serve as a container for the core
Explanation
The hollow form of nonmagnetic material found in the center of an aircore coil serves as a container for the core. The core is placed inside the hollow form to provide support and structure to the coil. It helps to maintain the shape and stability of the coil, ensuring that the windings are properly aligned and spaced. Additionally, the hollow form also helps to protect the core from external factors such as dust, moisture, and physical damage.
18.
Which of the following factors will NOT affect the value of inductance of a coil?
Correct Answer
C. Conductor tensility
Explanation
The value of inductance of a coil is not affected by the conductor tensility. Inductance is primarily determined by factors such as the number of coil turns, the diameter of the coil, and the core materials used. Conductor tensility refers to the ability of the conductor material to withstand stretching or bending without breaking. While conductor tensility is important for the durability and flexibility of the coil, it does not directly impact the inductance value.
19.
When the number of turns is increased in a coil from 2 to 4, the total inductance will increase by a factor of?
Correct Answer
D. Four
Explanation
When the number of turns in a coil is increased from 2 to 4, the total inductance will increase by a factor of four. This is because inductance is directly proportional to the square of the number of turns in a coil. So, when the number of turns is doubled from 2 to 4, the inductance will increase by a factor of four (2^2 = 4).
20.
Why do large diameter coils have greater inductance than smaller diameter coils, all other factors being the same?
Correct Answer
A. Large diameter coils have more wire and thus more flux
Explanation
Large diameter coils have more wire, which means there are more turns of wire in the coil. This increases the amount of magnetic field lines, or flux, that can pass through the coil. The increase in flux results in a higher inductance because inductance is directly proportional to the number of turns in a coil. Therefore, large diameter coils have greater inductance than smaller diameter coils, all other factors being the same.
21.
If the radius of a coil is doubled, its inductance is increased by what factor?
Correct Answer
D. Four
Explanation
When the radius of a coil is doubled, its inductance is increased by a factor of four. This is because the inductance of a coil is directly proportional to the square of its radius. So, when the radius is doubled, the inductance becomes four times larger.
22.
If the length of a coil is doubled while the number of turns is kept the same, this will have (a) what effect on inductance and (b) by what factor?
Correct Answer
B. (a) Decrease, (b) by 1/2
Explanation
When the length of a coil is doubled while the number of turns remains the same, the inductance will decrease. This is because inductance is directly proportional to the square of the number of turns and inversely proportional to the length of the coil. Therefore, when the length is doubled, the inductance will decrease by a factor of 1/2.
23.
A soft iron core will increase inductance because it has which of the following characteristics?
Correct Answer
D. High permeability and low reluctance
Explanation
A soft iron core will increase inductance because it has high permeability, which means it can easily allow the magnetic flux to pass through it. Additionally, it has low reluctance, which means it offers minimal opposition to the flow of magnetic flux. These characteristics of high permeability and low reluctance result in a higher inductance value for the soft iron core.