Electricity 3

Question 1

AC is ______ compared to DC.

Answer 1

more versatile and cheaper to produce

Question 2

Most of the power loss over great distance is from _____ and ______.

Answer 2

heat loss and internal resistance of the source.

Question 3

P=I²R, Heat loss equals

Answer 3

current squared times resistance

Question 4

AC generators use physical motion and magnetism to produce

Answer 4

electricity.

Question 5

The AC waveform shows magnitude and direction of voltage and current with respect to

Answer 5

time.

Question 6

Fluctuating DC waveforms follow the same shape as AC waveforms except they never fall below

Answer 6

the horizontal axis.

Question 7

When an AC waveform goes through 360 degrees, it is said to have completed

Answer 7

one cycle.

Question 8

AC amplitude equals

Answer 8

peak value.

Question 9

Effective values are _____ times peak values.

Answer 9

.707

Question 10

Phase means

Answer 10

the relationship between voltage and current.

Question 11

Frequency is

Answer 11

cycles per second.

Question 12

The concentration of current flow near the surface of a conductor is called ________ and increases resistance.

Answer 12

the skin effect

Question 13

An electric current is made up of ______.

Answer 13

many free electrons moving in the same direction

Question 14

The magnitude of induced EMF is proportional to _____, _____, and ______.

Answer 14

the strength of the magnetic field, length of the conductor, and speed of the cutting action.

Question 15

The strength and direction of the magnetic field around a conductor through which AC is flowing, depends on the _____ and _____.

Answer 15

magnitude and direction of the current

Question 16

EMF is determined by ______ and ______.

Answer 16

frequency and amplitude

Question 17

If a conductor is coiled, a _____ emf is produced.

Answer 17

greater

Question 18

If Inductance (L) or Capacitance (C) is present in a circuit, current is

Answer 18

limited.

Question 19

Inductors are also called

Answer 19

chokes or coils.

Question 20

XL=

Answer 20

2πfl

Question 21

A coil is said to be saturated when

Answer 21

even large changes in current cannot increase flux.

Question 22

Sometimes dots are used to indicate on transformers

Answer 22

in-phase terminals of the windings.

Question 23

When secondary current in a transformer is increased,

Answer 23

so does the current in the primary.

Question 24

When very little current flows in the secondary windings in a transformer, the voltage and current in the primary and secondary are

Answer 24

90 degrees out of phase.

Question 25

The unit of capacitance is the

Answer 25

farad.

Question 26

The capacitance of a capacitor is determined by _____, _____, and _____.

Answer 26

material of the dielectric, the surface area of the plates, and the distance between the plates.

Question 27

The voltage applied to a capacitor ____ current by 90 degrees.

Answer 27

lags

Question 28

In a purely resistive circuit, the power factor equals

Answer 28

1.