A.C. Theory, Lvl 1: Lesson #1- Understanding inductance and How it affects a circuit

Question 1

The direction of induced ? flow through a conductor is determined by the direction of the magnetic field surrounding the conductor and the direction the conductor is traveling through the magnetic field.

Answer 1

Current

Question 2

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

Answer 2

Voltage

Question 3

Whenever current flows through a conductor, a ? is created around the conductor.

Answer 3

Magnetic field

Question 4

When no current flows in a conductor, free electrons move ? , and their magnetic fields cancel.

Answer 4

at random

Question 5

When current flows in a conductor, a magnetic field is produced. As free electrons move in one direction, their individual magnetic fields ? .

Answer 5

add together

Question 6

The important factors needed for generation of an induced voltage are a conductor, a magnetic field, and ? .

Answer 6

relative motion

Question 7

As current flow decreases, the magnetic field surrounding the conductor will ? .

Answer 7

decreases

Question 8

As the current passing through a coil increases, the magnetic field around the coil will ? .

Answer 8

increases

Question 9

Whenever an electric current flows through a conductor, a magnetic field is formed ? the conductor.

Answer 9

around

Question 10

? Law states that an induced voltage or current opposes the motion that causes the induced voltage or current.

Answer 10

Lenzs

Question 11

Inductors always oppose a change of ? .

Answer 11

current

Question 12

Counter Electromotive Force is sometimes called back EMF, and CEMF is ? out-of-phase with the applied voltage.

Answer 12

180°

Question 13

CEMF ? the applied EMF when current is increasing and ? the applied EMF when current is decreasing.

Answer 13

subtracts from / adds to

Question 14

List factors that work in combination to affect the inductance produced by an inductor.

Answer 14

-Cross sectional area of the core
-Permeability of the core material
-Spacing between the turns

Question 15

The rate of current change in an inductive circuit can be described as a(n) ? curve.

Answer 15

exponential

Question 16

How many time constants does it take for current to reach its maximum value in an inductive circuit?

Answer 16

5

Question 17

At what percentage is the current after one time constant when the circuit is first energized?

Answer 17

63.2% of maximum

Question 18

The unit of inductance is the ? , and inductance is represented by the letter ? .

Answer 18

henry / L

Question 19

If a change of one ampere in one second causes one volt to be induced, you have ? of inductance.

Answer 19

one henry

Question 20

In high frequency applications, ? inductors are used because of eddy current loss and hysteresis loss in the core material.

Answer 20

air core

Question 21

In the formula for inductance, match the letter to what it represents.

Answer 21

Cross sectional area of the core = A
Length of the core used = I
Number of turns of wire = N
Permeability of the type of core material used = μ

Question 22

Inductance will ? with an increase in the cross sectional area of the core.

Answer 22

Increase

Question 23

Inductance is ? proportional to the length of the core used

Answer 23

inversely

Question 24

Inductance will ? with an increase in the number of turns of wire.

Answer 24

increase

Question 25

Inductance is ? proportional to the permeability of the type of core material used

Answer 25

directly

Question 26

What is the formula for determining the time constant in an inductive circuit?

Answer 26

Question 27

Given the formula for determining the counter EMF (induced voltage of a coil), drag the variables to the statement they represent.

Answer 27