Question 1

The polarity of the induced voltage is determined by the polarity of the magnetic field in relation to the direction of movement.

Accepted Answer

According to Faraday's Law, the induced voltage is directly proportional to the rate of change of magnetic flux and the polarity of the induced voltage is determined by the polarity of the magnetic field in relation to the direction of movement. Specifically, the direction of the induced voltage is such that it opposes the change in magnetic flux that produced it, in accordance with Lenz's Law.

Question 2

When a resistive load is suddenly connected to a source of direct current, the current will instantly ____.

Accepted Answer

When a resistive load is suddenly connected to a source of direct current, the current will rise to its maximum value (as per Ohm's law, I = V/R) and then stabilize at a lower value based on the resistance of the load.

Question 3

If a conductor cuts magnetic lines of flux at a rate of 1 V, a voltage of 1 Wb/s will be induced.

Accepted Answer

The correct unit for the induced voltage is volts (V), not webers per second (Wb/s), which is a unit of magnetic flux change rate, not voltage.

Question 4

The exponential curve can often be found in nature.

Accepted Answer

The exponential curve can be found in various natural phenomena such as the growth of populations, the decay of radioactive materials, the spread of diseases, and the accumulation of compound interest.

Question 5

A device often used to prevent induced voltage spikes when the current flow through an inductor is stopped is the ____.

Accepted Answer

The device often used to prevent induced voltage spikes when the current flow through an inductor is stopped is a diode. When the current through the inductor is suddenly interrupted, the magnetic field collapses, and a voltage spike is generated across the inductor. Placing a diode in parallel with the inductor provides a path for the induced current to flow, thereby preventing the voltage spike.

Question 6

The important factors concerning magnetic induction are a magnetic field, movement, and polarity.

Accepted Answer

The important factors concerning magnetic induction are a magnetic field, movement, and electrical conductivity. Polarity is not a factor in the basic principle of magnetic induction; instead, the movement of a conductor through a magnetic field or a changing magnetic field around a conductor induces an electrical current.

Question 7

A(n) ____ diode has a forward voltage drop of approximately 0.7 V regardless of the current flowing through it.

Accepted Answer

The given description matches that of a silicon diode.

Question 8

The time necessary for current in an inductor to reach its full Ohm's law value, called the R-L time constant, can be computed using the formula L = H / R.

Accepted Answer

The formula for the R-L time constant is actually T = L / R.

Question 9

A coil has an inductance of one ____ when a current change of one ampere per second results in an induced voltage of one volt.

Accepted Answer

The unit of inductance is the henry (H). A change in current of one ampere per second results in an induced voltage of one volt in a coil with an inductance of one henry.

Question 10

The principle of magnetic ____ states that whenever a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor.

Accepted Answer

The principle described in the question is known as electromagnetic induction, which states that a voltage (or electric potential difference) is induced in a conductor as it moves through a magnetic field or as the magnetic field around it changes. Option A, induction, correctly describes this principle. Option B, conduction, refers to the transfer of electrical charge through a material, but it is not directly related to the topic of the question. Option C, reduction, refers to a decrease in the amount or intensity of something, and option D, fluctuation, refers to irregular changes or variations, but neither of these options accurately describe the principle of electromagnetic induction.

Question 11

Iron-core inductors cannot be used for high-frequency applications because of ____ loss and hysteresis loss in the core material.

Accepted Answer

Iron-core inductors have high eddy current and hysteresis losses at high frequencies due to the core material's magnetic properties.

Question 12

The exponential curve describes a rate of certain occurrences and is divided into four time constants.

Accepted Answer

The exponential curve describes a rate of growth or decay, but it is not divided into four time constants. The concept of time constants is more specifically related to the response of systems (like electrical circuits or mechanical systems) to external changes, and it describes the time it takes for the system to change significantly (e.g., to reach a certain percentage of its final value), not divisions of an exponential curve.

Question 13

Each time constant in an exponential curve is equal to ____% of some value.

Accepted Answer

Each time constant in an exponential curve is equal to 63.2% of some value. This is because, in exponential growth or decay, the value at each time t is equal to the initial value multiplied by e raised to the power of t divided by the time constant. When t equals the time constant, the value will be 63.2% of the initial value. Therefore, option D is the correct choice.

Question 14

A device that uses the collapsing magnetic field of an inductor to produce a very low voltage is the electric-fence charger.

Accepted Answer

An electric-fence charger actually uses the collapsing magnetic field of an inductor to produce a very high voltage, which is necessary to deliver a noticeable shock through the fence.

Question 15

A device that can be used for spike suppression in either direct- or alternating-current circuits is the metal oxide varistor (MOV).

Accepted Answer

The metal oxide varistor (MOV) is indeed a device used for spike suppression in both direct and alternating current circuits.

Question 16

Three factors determine the amount of voltage that will be induced in a conductor: the number of turns of wire, the strength of the magnetic field (flux density), and the ____ of the cutting action.

Accepted Answer

The amount of voltage induced in a conductor is directly proportional to the speed of the cutting action. This is because a faster movement of the conductor through the magnetic field results in more lines of magnetic flux being cut per unit time, leading to a higher voltage induced. The number of turns of wire and the strength of the magnetic field also affect the induced voltage, but they are not directly related to the cutting action.

Question 17

A(n) ____ occurs when the current flow through an inductor stops, and the current decreases at an exponential rate also.

Accepted Answer

This is known as a voltage spike, also referred to as a back-EMF or flyback voltage, and occurs when the current flowing through an inductor is suddenly interrupted, causing a high voltage pulse in the opposite direction of the original current flow. This can be problematic in electronic circuits and can be mitigated with diodes or other protective measures.

Question 18

Inductance is measured in units called the henry and is represented by the letter H.

Accepted Answer

The answer of Inductance is measured in units called the...

Question 19

In magnetic measurement, ____ lines of flux are equal to one weber (Wb).

Accepted Answer

The answer of In magnetic measurement, ____ lines of flux...

Question 20

The induced voltage is proportional to the rate of change of current (speed of the cutting action).

Accepted Answer

This is known as Faraday's law of electromagnetic induction. The induced voltage is directly proportional to the rate of change of current or the speed of the cutting action.

Quiz 2: Magnetic Induction