Answer to Question #199864 in Electrical Engineering for richard gate

Question

i. In your own words explain why current is transmitted over long distance as alternating current (ac) and not as direct current (dc)

ii. Compare and contrast a direct current circuit and an alternating current circuit using graphs.

iii. Using your knowledge of the concept of expressing sinusoids in terms of phasors in alternating current (ac) demonstrate how you will obtain the voltages v and V, the phasor current I and sketch phasor diagram if a circuit has a series combination of R=40Ω and L=80 mH and has a current

 i=2.0 Cos(500t+10o) (A)

Answer 1

i) The voltage lost along the wires is proportional to the resistance of the wires and the current, therefore the higher the current, the more voltage (and hence power) is lost. It is possible. The issue with long-distance electricity transmission is loss.

ii)

iii) $I=2cos(500t+10^0)A$

In phasor form w=500t

$I=\frac{2}{\sqrt{2}} \angle 10^0 V =1.414 \angle 10^0 A$

$V_R=IR=1.414 \angle 10^0 *40= 56.56 \angle10^0 V$

$V_L=IX_L=1.414 \angle10^0 * j *500+sin10 =56.56\angle100^0 V$

The total voltage

$V=V_R+V_L=56.56 \angle 10^0+56.56 \angle 100^0=79.98 \angle 55^0 V$