Alternating Current

Question 1

Sinusoidal AC

Answer 1

V = V0 sin(ωt)
I = I0 sin(ωt)

V rms = V0 / √2
I rms = V0 / √2

ωt = 2πft = 2πt / T

Question 2

Define root-mean-square (rms) of ac

Answer 2

The rms of an ac is the value of the steady current that will dissipate heat at the same average rate as the alternating current in a resistive load.

Question 3

Power equations for ac

Answer 3

P = IV = I0V0 sin²(ωt)
P = I²R = I0²R sin²(ωt)
P = V²/R = (V0²/R) sin²(ωt)

P0 = I0V0 = I0²R = V0² / R

mean P = 1/2 P0
mean P = Irm² R
mean P = Vrms² /R

Question 4

Purpose of laminated core

Answer 4

To reduce energy loss due to heat by reducing induced/eddy currents in the core.

Question 5

Purpose of soft-iron core

Answer 5

To channel the magnetic field from the primary coil to the secondary coil through the core to increase flux linkage ( minimize flux leakage )

Question 6

Rectification

Answer 6

Process of converting ac to dc