Magnetic Induction

Question 1

What is the principle of magnetic induction?

Answer 1

Whenever a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor

Question 2

The polarity of induced voltage is determined by what?

Answer 2

The polarity of the magnetic field in relation to the direction of movement.

Question 3

What is Fleming’s left-hand generator rule?

Answer 3

A trick for determining the direction of current flow through an armature when the direction of motion and polarity of the magnetic field is known.

Question 4

How do you use Fleming’s left-hand generator rule?

Answer 4

Place pointer finger, thumb, and middle finger at right angles to each other.
Remember that the pointer finger represents the direction of the field flux, the thumb represents the direction of the flux, and the middle finger represents the direction of the current induced by the armature.

Question 5

What are three important factors for electromagnetic induction?

Answer 5

A conductor, a magnetic field, and relative motion

Question 6

How do AC generators operate?

Answer 6

A coil of wire is held stationary while a magnet is moved through the coil. As the magnet is moved, the lines of flux cut through the windings of the coil and induce a voltage in them.

Question 7

What three factors determine the amount of voltage that will be induced in a conductor?

Answer 7

1. The number of wire turns
2. The strength of the magnetic field (flux density)
3. The speed of the cutting action

Question 8

What does Lenz’s law state?

Answer 8

An induced voltage or current opposes the motion that causes it.

Question 9

What would happen to current if a resistor was replaced with an inductor?

Answer 9

The current would have a harder time reaching its maximum value.

Question 10

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

Answer 10

Proportional

Question 11

What is the exponential curve?

Answer 11

A curve found in nature that tells the rate at which current can rise or fall in an inductor.

Question 12

How many time constants is an exponential curve divided into? What % does the current rise during each time constant?

Answer 12

Five constants. 63.2% of some stated value.

Question 13

What is the unit of measurement for inductance? This unit name is in honor of _________

Answer 13

henry (H) Joseph Henry

Question 14

What is the difference between digital and analog

Answer 14

Digital goes from 0 or 1. Analog fluctuates between 0 and 1. Analog will never reach 0 because fluxes will always be cut in half.

Question 15

A coil wound on a nonmagnetic core material (ex. wood or plastic) is referred to as an __________

Answer 15

Air-core inductor

Question 16

A coil wound on a core made of magnetic material (ex. iron) is referred to as an ____________

Answer 16

Iron-core inductor

Question 17

Which type of inductor produces more inductance with fewer turns? Why?

Answer 17

Iron-core. The core material provides a good magnetic path.

Question 18

Besides core material, what is another factor that determines inductance?

Answer 18

How far coil windings are separated from each other. The less separated the coil windings are, the more inductance the core will produce.

Question 19

What is the R-L time construct? What is the formula?

Answer 19

The time necessary for current in an inductor to reach its full Ohm’s law value. Formula for it is T = L/R

Question 20

What is a voltage spike?

Answer 20

A momentary increase of voltage lasting 2 nanoseconds or less.