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Flashcards in Electricity 3 Deck (29)
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1

AC is ______ compared to DC.

more versatile and cheaper to produce

2

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

heat loss and internal resistance of the source.

3

P=I2R, Heat loss equals

current squared times resistance

4

AC generators use physical motion and magnetism to produce

electricity.

5

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

time.

6

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

the horizontal axis.

7

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

one cycle.

8

AC amplitude equals

peak value.

9

Effective values are _____ times peak values.

.707

10

Phase means

the relationship between voltage and current.

11

Frequency is

cycles per second.

12

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

the skin effect

13

An electric current is made up of ______.

many free electrons moving in the same direction

14

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

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

15

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

magnitude and direction of the current

16

EMF is determined by ______ and ______.

frequency and amplitude

17

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

greater

18

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

limited.

19

Inductors are also called 

chokes or coils.

20

XL=

2πfl

21

A coil is said to be saturated when

even large changes in current cannot increase flux.

22

Sometimes dots are used to indicate on transformers

in-phase terminals of the windings.

23

When secondary current in a transformer is increased, 

so does the current in the primary.

24

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

90 degrees out of phase.

25

The unit of capacitance is the

farad.

26

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

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

27

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

lags

28

In a purely resistive circuit, the power factor equals

1.

29