DC Theory Lesson 6

An electrical generator is a device that converts electrical energy into mechanical energy.

Select one:

True

False

The basic theory of electrical generation was discovered by ? in 1831.

a. Andre Ampere

b. Charles Coulomb

c. Georg Simon

d. Michael Faraday

DC current flows in one direction in a conductor, while AC current flows in both directions.

Select one:

True

False

Inducing a voltage into a conductor by passing it through a magnetic field is called ? .

a. electromagnetic induction

b. electrostatic induction

c. relative motion

d. reluctance

There must be ? between the conductor and the magnetic field in order to have a voltage induced.

a. electromagnetic induction

b. relative motion

c. reluctance

d. resistance

In order to induce one volt into a single conductor, ? lines of flux must be cut in one second.

a. 10,000

b. 1,000,000

c. 10,000,000

d. 100,000,000

The ? makes up all non-rotating electrical parts of a generator or motor.

a. brushes

b. commutator

c. slip rings

d. stator

At the start, or 0° position, of the armature rotation cycle, induced EMF is ? volts.

a. 0

b. 0.5

c. 1

d. 2

The magnitude of voltage produced by electromagnetic induction can be increased by

increasing the number of loops in the wire that cuts the field.

Select one:

True

False

Voltage can also be increased by making the magnetic field stronger or by increasing the

? of the conductor cutting flux lines in the magnetic field..

a. material

b. resistance

c. size

d. speed

Which of the following is a source of mechanical energy used to turn the rotor of a generator?

a. Fossil fuels

b. Manpower

c. Water

d. Wind

e. All of the above

Which of the sources of mechanical energy must be converted into another form in order to turn the rotor of a generator?

a. Fossil fuels

b. Manpower

c. Water

d. Wind

Most modern commercial electric power is produced by electromagnetic induction.

Select one:

True

False

Electrical generators produce DC voltage.

Select one:

True

False

How is the voltage removed from an AC generator and applied to an external circuit?

a. Commutators are used.

b. Inverters are used.

c. Slip rings and brushes are used.

d. Stators are used.

In DC machines, a(n) ? is used instead of slip rings.

a. coil

b. commutator

c. inverter

d. stator

A commutator converts the DC generated in the armature winding to an AC output from the generator.

Select one:

True

False

What rule relates motion, direction of magnetic field, and direction of current flow for electromagnetic induction?

a. The left hand rule for conductors

b. The left hand rule for generators

c. The right hand rule for conductors

d. The right hand rule for generators

Applying the left hand rule for generators, the middle finger indicates the direction of current induced into the ? .

a. armature

b. brushes

c. commutator

d. stator

Electromagnetic induction can also be accomplished by moving a(n) magnetic field

across a(n) conductor.

Select one:

True

False

Because the commutator is a split ring with each half insulated from the other, and the brushes are fixed, each brush is always connected to the loop going in the same direction.

Select one:

True

False

How much voltage is induced into the loop at the one-half turn or 180-degree position of the rotation?

a. 0 V

b. 1 V

c. 2 V

d. 5 V

At what point(s) in the rotation of the armature is the maximum positive voltage induced?

a. One-eighth turn

b. One-quarter turn

c. One-half turn

d. Three-quarter turn

At what degree of rotation in a generator cycle is the maximum negative voltage produced?

a. One-eighth turn

b. One-quarter turn

c. One-half turn

d. Three-quarter turn

The magnitude of the voltage being produced by electromagnetic induction is determined by how many lines of magnetic flux are being cut by the conductor per second.

Select one:

True

False

In DC motors and generators, the armature is the stator and the field is the rotor.

Select one:

True

False

The armature is always the rotor on DC machines that have a commutator.

Select one:

True

False

A commutator will have ? pair(s) of segments for each coil in the armature.

a. 1

b. 2

c. 3

d. 4