Question

A 20 Ohm resistance is connected

across the secondary winding of a
single-phase power transformer
whose secondary voltage is 150 V.
Calculate the primary voltage if the
supply current is 5 A, neglecting
losses.

Answer 1

Answer: 225 V

Step-by-step explanation:

Given:

Secondary voltage,V2 = 150v

Resistance is connected across secondary winding,∴R2 = 20Ω

Supply current, ie, I1 = 5A

`\text{Now, secondary current,} \ $I_(2)=(V_(2))/(R_(2))=(150)/(20)=7.5$$$\therefore I_(2)=7.5 \mathrm{~A}$$For Transformers, we have $(N_(2))/(N_(1))=(V_(2))/(V_(1))=(I_(1))/(I_(2))$ so, Taking $(N_(2))/(N_(1))=(l_(1))/(l_(2))$ inserting all given \& obtained values, we get $(N_(2))/(N_(1))=(5)/(7.5)$$$\therefore \text { Turns ratio }=(N_(1))/(N_(2))=(7.5)/(5)=(3)/(2)=3: 2$$`

`\text{Again taking,}(N_(1))/(N_(2))=(V_(2))/(V_(1))$ \\So, \\$V_(1)=(N_(1))/(N_(2)) V_(2)\\$ inserting all values, we get, $V_(1)=(7.5)/(5) * 150=225$\\Therefore, \fbox{Primary voltage, {$V_(1)=225 \mathrm{~V}$}}`