Question

A step-down transformer has a 120 Vrms primary voltage applied. A 12 Vrms voltage is measured at the secondary. Assuming the transformer can be considered ideal, determine the turns ratio, n. If a 1  load is attached to the secondary of this transformer, what is the rms load current? What is the rms primary current?

Answer 1

(a). The rms load current is 1.08 A.

(b). The rms primary current is 0.108 A.

Step-by-step explanation:

Given that,

Primary voltage = 120

Secondary voltage = 12

Load = 10 ohm

We need to calculate the number of turns in primary and secondary coil

Using formula of voltage

`(V_(1))/(V_(2))=(N_(1))/(N_(2))`

Put the value into the formula

`(N_(1))/(N_(2))=(120)/(12)`

`(N_(1))/(N_(2))=10`

`(N_(2))/(N_(1))=0.1`

We need to calculate the resistance

Using formula of resistance

`R=10*((N_(1))/(N_(2)))^2`

Put the value into the formula

`R=10*(10)^2`

`R=1000\ \Omega`

We need to calculate the current in primary coil

Using formula of current

`I_(1)=(120-12)/(1000)`

`I_(1)=0.108\ A`

We need to calculate the current in secondary coil

Using formula of current for secondary coil

`(I_(1))/(I_(2))=(N_(2))/(N_(1))`

`I_(2)=I_(1)*(N_(1))/(N_(2))`

Put the value into the formula

`I_(2)=0.108*10`

`I_(2)=1.08\ A`

Hence, (a). The rms load current is 1.08 A.

(b). The rms primary current is 0.108 A.