Electrical Fundamentals Module 3 Quiz

In a basic AC generator, this position refers to when the conductor is moving parallel to the magnetic field lines, resulting in no cutting of lines and therefore no induced electromotive force (EMF).

At this position, the conductor is cutting directly across the magnetic field lines, leading to the maximum induced voltage.

As the conductor continues to rotate, it cuts fewer lines of force, resulting in a decrease in the induced voltage until it reaches zero at Position C.

This position marks the point where the conductor is again cutting directly across the field lines, resulting in the maximum induced voltage, but with a polarity change compared to Position B.

A graphical representation of the voltage induced in an AC generator over time, showing how the voltage rises and falls in a sinusoidal pattern.

The process of generating an alternating current (AC) using a loop of wire rotating within a magnetic field.

Electromotive force (EMF) is generated when a conductor moves through a magnetic field and cuts lines of force. The strength of the induced EMF is directly proportional to the rate at which the conductor cuts the lines of force.

The direction of the induced current in a conductor moving through a magnetic field is determined by the direction of motion and the direction of the magnetic field.

The electrical resistance of a material is inversely proportional to its cross-sectional area. This means that a larger cross-sectional area leads to lower resistance.

Eddy currents are circular currents induced within a conductor due to a changing magnetic field. They are a form of energy loss and generate heat.

Laminations are thin sheets of magnetic material, insulated from each other, which make up the core of an electrical machine, like a generator.

Laminating the core reduces eddy current losses because it increases the resistance to those currents. It effectively breaks up the path for eddy currents.

Hysteresis loss is the energy lost in a magnetic material due to the friction between magnetic domains as they align and realign with a changing magnetic field.

Hysteresis losses are minimized by using silicon steel laminations, which are heat-treated to reduce the friction between magnetic domains.

The output voltage of a DC generator depends on three factors: the number of loops in the armature, the armature's speed, and the magnetic field strength.

Changing the speed of the armature is usually the most practical way to adjust the output voltage of a DC generator.

The frame of a DC generator that houses and supports other components, such as the armature, commutator, and field coils. It also completes the magnetic circuit between the poles.

A rotating cylindrical structure that consists of windings and is responsible for generating the DC voltage. It houses insulated copper wires wound on a metal core.

A segmented device that converts alternating current (AC) generated in the armature into direct current (DC) for use by external circuits.

Carbon rods used in the DC generator to make contact with the commutator segments and provide a path for current flow from the armature to the external circuit.

Thin sheets of metal stacked together, used as the core in the field poles to reduce energy losses due to eddy currents.

It's a multi-layered wire coil that is wound around a core. In a DC generator, the field coil creates an electromagnet that produces a magnetic field to interact with the armature, generating electricity.

Also known as Magnetic Pole, it's what the field coil is wound around. It's a horseshoe-shaped piece of iron that serves as a conductor for the magnetic field produced by the field coil.

The property of being easily magnetised, and used to describe the high permeability, making it easily magnetized by the field coils, facilitating efficient magnetic circuit formation.

The armature in a DC motor rotates in the opposite direction when the field winding polarity is reversed.

The armature field in a DC motor distorts the main field, shifting the neutral plane backwards opposite to the direction of rotation.

The shift in the neutral plane in a DC motor requires shifting the brushes to maintain proper commutation and prevent sparking.

Compensating windings and interpoles are used to cancel the armature reaction in DC motors by counteracting the distorting effect of the armature field.

Compensating windings in DC motors are similar to those used in generators and are designed to counteract the armature reaction.

Interpoles in DC motors have the same polarity as the main pole following the direction of rotation, unlike in generators.

Interpoles in DC motors automatically adjust the flux to correct commutation as the load varies, eliminating the need for brush shifting.

Compensating windings are more expensive than interpoles, so most large DC motors rely on interpoles to correct armature reaction.

A type of DC motor where the field winding is connected in series with the armature. This results in high starting torque and a wide speed range, but also makes it prone to overspeeding when unloaded.

The turning force produced by a motor. In a series motor, high torque is generated because the field winding carries the full armature current.

A variable resistor used to control the speed of a series motor by adjusting the current flowing through the armature winding.

The field winding in a series motor is typically made with a few turns of thick wire, which can carry the full armature current. This produces a strong magnetic field necessary for high torque.

A DC motor type where the field winding is connected in parallel with the armature. This results in a more constant speed compared to a series motor.

A DC motor type where both series- and shunt-connected field windings are used. This offers a combination of high starting torque and relatively constant speed.

A DC motor type where the field winding is supplied by a separate external source, typically a battery or power supply. This allows for precise control of the motor's speed and torque.

A DC motor type that uses permanent magnets to provide the magnetic field instead of field windings. This eliminates the need for a separate field winding and often results in more compact designs.

A combined electric starter and generator, typically used in small turbine engines, providing both starting power and electrical generation.

A starter-generator eliminates the separate clutch assembly found in conventional systems, so it's always engaged and spinning with the engine.

Starter-generators use a quill shaft to connect to the engine, allowing for smooth and accurate power delivery.

Starter-generators offer significant weight savings compared to traditional starter and generator setups, making them ideal for lightweight aircraft.

Starter-generators have two sets of field windings and one armature winding, designed for both starting and generating functions.

In starter mode, high current flows through both field windings and the armature, providing high power for starting the engine.

In generator mode, current flows through the shunt winding, creating a magnetic field that induces voltage into the armature.

Starter-generators are commonly used in turbine engines where weight and efficiency are paramount.