Resist. & Cap.

Question 0

Total voltage is equal to the _______ of the voltages across _______ _______ of the circuit.

Answer 0

Sum, all parts

Vt = V1 + V2 + V3

Question 1

Current in each part is _______ to the current in _______ _______ part and _______ to total current.

Answer 1

Equal, every other, equal.

It = I1 = I2 = I3

Question 2

In a purely inductive circuit (zero resistance) the current will _______ _______ the voltage by _______ _______.

Answer 2

Lag behind, 90 degrees

Question 3

For resistance the voltage and the current are ________ ________.
For inductance the voltage and current are _____ _____ _____ _____ phase.

Answer 3

In phase, 90 degrees out of

Question 4

In a purely inductive circuit no _______ is dissipated. Energy is stored in the ________ ________ and then returned to the circuit.

Answer 4

Power, magnetic field.

Question 5

When Ohm’s law is applied to inductance, the relationship between voltage and current is called _______ instead of ________.

Answer 5

Reactance, resistance

Question 6

The symbol for reactance is ______.

Answer 6

X

Question 7

The symbol for inductance is ______.

Answer 7

L

Question 8

The larger the inductance the larger the _______.

Answer 8

Reactance

Question 9

The measurement for inductance is the ________.

Answer 9

Henry

Question 10

In an AC circuit the higher the _______ the _______ the flux changes. This means that the reactance ________ as the frequency ________.

Answer 10

Frequency, faster.

Increases, increases.

Question 11

The symbol for the factor 2πf is _____.

Answer 11

ω

Question 12

The larger the capacitance, the _______ the reactance

Answer 12

Smaller.

Question 13

The larger the frequency, the ________ the reactance.

Answer 13

Smaller

Question 14

The formula to find capacitive reactance is:

Answer 14

Xc = 159,000 / f x C

Question 18

What is the symbol we use to remind ourselves that voltage leads the current by 90 degrees?

Answer 18

j

Question 19

The formula for adding voltages in a series AC circuit that are not in phase is:

Answer 19

Vt²=Vr²+Vc² _

Question 20

To find total impedance in a series AC circuit the formula is:

Answer 20

Z² = R²+Xc² _
Or:
Z = √R² + Xc²

Question 21

To find impedance by trigonometry, the formula is:

Answer 21

cos θ = a /h
Or:
cos θ = R/Z

Question 22

To find power in an AC series circuit the formula is :

Answer 22

W = V x I x cos θ
Or 
W = V x I x PF
Or 
W = l²R

Question 23

There is a circuit with a 5Ω resistor connected in series with a capacitor with a reactance of 12Ω @ a frequency of 60Hz. A series current of 1A produces a voltage drop of 5V across the resistor & 12V across the capacitor. What is the power factor (PF)?

Answer 23

PF = R / Z
PF = 5 / 13 = 0.3846
.03846 x 100% = 38.5% leading

Question 24

There is a circuit with a 5Ω resistor connected in series with a capacitor with a reactance of 12Ω @ a frequency of 60Hz. A series current of 1A produces a voltage drop of 5V across the resistor & 12V across the capacitor. What is the power?

Answer 24

W = V x I x PF
W = 13 + 1 + 0.385 = 5W.
Check:
W = l²R = (1)² x 5 =5W

Question 25

There is a circuit with a 5Ω resistor connected in series with a capacitor with a reactance of 12Ω @ a frequency of 60Hz. A series current of 1A produces a voltage drop of 5V across the resistor & 12V across the capacitor. What is the Vt?

Answer 25

Vt²=Vr²+Vc² 
Vt² = 5²+12² 
Vt² = 25 + 144
Vt² = 169
 Vt² = √ 169 = 13

Question 26

There is a circuit with a 5Ω resistor connected in series with a capacitor with a reactance of 12Ω @ a frequency of 60Hz. A series current of 1A produces a voltage drop of 5V across the resistor & 12V across the capacitor. What is the Z?

Answer 26

Z = √R² + Xc²
Z= √5²+12² 
Z =  √25+ 144
Z =  √169 
Z = 13Ω

Question 27

There is a circuit with a 5Ω resistor connected in series with a capacitor with a reactance of 12Ω @ a frequency of 60Hz. A series current of 1A produces a voltage drop of 5V across the resistor & 12V across the capacitor. What is the phase angle?

Answer 27

cos θ = R / Z θ = 5 / 3 = 0.3846 acos = 67 θ = 67° (approx)

Question 28

``` A capacitance of 4 μF & a resistance of 30 Ω are connected in series across a 100V 1kHz ac source. Find Xc, Z, & It. Givens: C = 4 μF R = 30Ω V = 100V f = 1 kHz ```

Answer 28

Xc = 159,000 / f x C ⇒ 159,00 / 1000 x 4 ⇒ 159 / 4 = 40Ω (approx.) Z = √R²+Xc² ⇒ √30²+40² ⇒ √900 + 1600 ⇒ √2500 = 50Ω Vt = It x Z (same as V = IR) ⇒ 100 = It x 50 ⇒ It = 100/50 = 2A

Question 29

``` A capacitance of 4 μF & a resistance of 30 Ω are connected in series across a 100V 1kHz ac source. Find Vr, Vc, & θ. Givens: C = 4 μF Χc = 40Ω R = 30Ω. Z = 50Ω V = 100V. It = 2A f = 1 kHz ```

Answer 29

Since It = Ir = Ic =2A. cos θ =R / Z = 30/50= .06000 Vr = Ir x Rr. acos 0.6000 = 53.13 Vr = 2 x 30 = 60V. θ = 53° (approx) Vc = Ic x Xc Vc = 2 x 40 = 80V

Question 30

``` A capacitance of 4 μF & a resistance of 30 Ω are connected in series across a 100V 1kHz ac source. Find PF & W. Givens: C = 4 μF Χc = 40Ω R = 30Ω. Z = 50Ω Vt = 100V. It = 2A f = 1 kHz ```

Answer 30

``` PF = R/Z. W= V x I x PF = 100 x 2 x 0.6 = 120W PF = 30/50= 0.6000. Check: W = l²R = (2)² x 30 = 120W PF = 0.6000 x100 = 60% leading ``` In this series circuit, the total current of 2A leads the total voltage of 100V by 53°.