Electric Generators: Basic Principles

Which statement best defines an electric generator?

• A device that converts electrical energy to mechanical energy

• A device that converts mechanical energy to electrical energy

• A device that stores electrical energy in a magnetic field

• A device that amplifies voltage without moving parts

In the basic construction of an electric generator, where are the wire loops placed to enable EMF induction?

• Inside an electrostatic field

• In a strong magnetic field

• Around a heated filament

• Between two grounded plates

What is the primary purpose of winding the wire around an iron core in a generator?

• To reduce resistance of the wire

• To increase the strength of the magnetic field

• To prevent thermal expansion

• To convert AC to DC

Identify the component formed by the iron and the wires in an electric generator.

• Commutator

• Armature

• Stator windings

• Slip rings

How is the armature mounted in a generator?

• Fixed in place to prevent motion

• Suspended to vibrate with the field

• Mounted so it can rotate freely in the magnetic field

• Clamped to the stator to maintain alignment

What is the effect of increasing the number of loops in the armature?

• It shortens the effective wire length and reduces EMF

• It increases wire length and therefore increases induced EMF

• It changes AC to DC without rectification

• It eliminates the need for a magnetic field

Consider the diagram showing a rectangular wire loop between two magnetic pole pieces with arrows labeled Up and Down on opposite sides of the loop. Based on this setup, what physical action is represented by these arrows?

• Alternating thermal expansion of the loop

• Opposite directions of current due to electrostatics

• Opposite motion of loop sides as the armature rotates

• Polarization of the iron core

Which orientation of the loop relative to the magnetic field yields zero induced current?

• Wire segments moving perpendicular to the field

• Wire segments moving parallel to the field

• Loop plane perpendicular to the velocity

• Loop stationary but tilted 45°

What is the waveform of the current produced by the rotating loop, as shown in the "Current v. Time" figure?

• Square wave alternating between ±Imax

• Triangular wave with linear rise and fall

• Sinusoidal wave alternating between positive and negative values

• Constant DC value with occasional spikes

Refer to the diagram showing the generator loop and the sinusoidal current vs. time graph. At what angular rotation of the loop does the induced current reverse direction?

• Every 90° of rotation

• Every 180° of rotation

• Only at 360° of rotation

• Randomly depending on speed