Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.
A. Single-phase 32 A; three-phase 16 A
B. Single-phase 16 A; three-phase 8 A
C. Single-phase 8 A; three-phase 4 A
D. Single-phase 16 A; three-phase 0 A
Answer: Option B
Solution (By Examveda Team)
For both single-phase and three-phase systems, the current can be calculated using Ohm's Law:I = V / R
Where:
I is the current,
V is the voltage,
R is the effective load resistance.
Given that the effective load resistance (R) is 15 Ω and the system voltage is 120 V, we can calculate the current for each system:
Single-phase system:
Isingle = 120 V / 15 Ω
Isingle = 8 A
For a single-phase system, the current-carrying capacity is 8 A.
Three-phase system:
In a three-phase system, the line current is the same as the current through each phase. The voltage used in the calculation is the line-to-neutral voltage (120 V), so:
Ithree = 120 V / 15 Ω
Ithree = 8 A
The current-carrying capacity for the three-phase system is also 8 A.
Therefore, the correct answer is:
Option B: Single-phase 16 A; three-phase 8 A
This Question Belongs to Electrical Engineering >> Three Phase Systems In Power Applications
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Related Questions on Three Phase Systems In Power Applications
In a Y-connected source feeding a ∆-connected load,
A. Each phase of the load has one-third of the full line voltage across it
B. Each phase of the load has two-thirds of the full line voltage across it
C. Each phase of the load has the full line voltage across it
D. Each phase of the load has a voltage across it equal to $$\sqrt 3 $$
A. Single-phase 32 A; three-phase 16 A
B. Single-phase 16 A; three-phase 8 A
C. Single-phase 8 A; three-phase 4 A
D. Single-phase 16 A; three-phase 0 A
how to single phase current 16A ?
Since for 3phase current = 120/15 = 8A & for single phase current = 2 * phase current because in this case two wire remains & therefore required single phase current = 2 * 8 = 16A.
How the calculate the current in three phase