AC circuits

Question 1

What is the objective of the AC circuits session?

Answer 1

Demonstrate a thorough understanding of the basic principles of AC circuits.

Question 2

What is created in a coil when a magnetic field rotates?

Answer 2

Electromotive force (emf)

Question 3

The magnitude of emf depends on what?

Answer 3

The position of the field

Question 4

What determines how quickly the voltage builds up in an AC circuit?

Answer 4

The speed of rotation

Question 5

What is the frequency of AC generation in the UK?

Answer 5

50 cycles per second (Hz)

Question 6

What is the time period (T) for one cycle if the frequency is 50 Hz?

Answer 6

20 ms

Question 7

What is the relationship between frequency (f) and time period (T)?

Answer 7

f = 1/T

Question 8

In a purely resistive circuit, how do current and voltage behave?

Answer 8

Current reaches a maximum when voltage reaches a maximum; they are in phase.

Question 9

In a purely inductive circuit, how does current relate to voltage?

Answer 9

Current lags voltage by 90 degrees.

Question 10

In a purely capacitive circuit, how does current relate to voltage?

Answer 10

Current leads voltage by 90 degrees.

Question 11

What is the angular velocity (ω) in terms of frequency (f)?

Answer 11

ω = 2πf rads/sec

Question 12

What does a phasor diagram represent in AC circuits?

Answer 12

The relationship between voltage and current and the angle between them.

Question 13

In an RLC series circuit, what is the total resistance to current called?

Answer 13

Impedance (Z)

Question 14

What is the formula for inductive reactance (X_L)?

Answer 14

X_L = ωL = 2πfL

Question 15

What is the formula for capacitive reactance (X_C)?

Answer 15

X_C = 1/ωC = 1/(2πfC)

Question 16

How do you calculate the current (I) in an RLC circuit?

Answer 16

I = V/Z

Question 17

What is true power (P) in AC circuits calculated as?

Answer 17

P = VIcosϴ

Question 18

In the example provided, what are the values of R, L, and C?

Answer 18

R = 10Ω, L = 50mH, C = 100uF

Question 19

What is the value of circuit impedance (Z) in the example?

Answer 19

Z = 18.97Ω

Question 20

What is the calculated circuit current (I) in the example?

Answer 20

I = 12.65A

Question 21

What is the angle (ϴ) between current and voltage in the example?

Answer 21

ϴ = 58.2 degrees

Question 22

What is the power factor of the circuit represented by?

Answer 22

cosϴ

Question 23

True or False: No true power is dissipated in a pure inductor or capacitor.

Answer 23

True

Question 24

Fill in the blank: The current is the reference phasor as it is common to all components in a _______.

Answer 24

series circuit