Question

A plug-in transformer, like that in Figure\(23.29\), supplies\(9.00{\rm{ }}V\)to a video game system.

(a) How many turns are in its secondary coil, if its input voltage is\(120{\rm{ }}V\)and the primary coil has\(400\)turns?

(b) What is its input current when its output is\(1.30{\rm{ }}A\)?

Short answer

1. Number of turns in its secondary coil is\(30\).
2. Input current value is \(9.75 \times {10^{ - 2}}\;A\).

Step-by-step solution

Definition of current  

Current is the term used to describe the rate at which charge moves with regard to time.

Given information and Formula to be used

a)

\(\begin{array}{l}{V_p} = 120\;V\\{V_s} = 9\;V\\{N_p} = 400\end{array}\)

Transformer equation,

\(\frac{{{V_s}}}{{{V_p}}} = \frac{{{N_s}}}{{{N_p}}}\)

b)

\(\begin{array}{l}{V_p} = 120\;V\\{V_s} = 9\;V\\{I_s} = 1.30\;A\end{array}\)

Transformer equation,

\(\frac{{{V_s}}}{{{V_p}}} = \frac{{{I_p}}}{{{I_s}}}\)

Number of turns in Secondary Coil 

a)

Consider the transformer equation,

\(\begin{array}{c}\frac{{{V_s}}}{{{V_p}}} = \frac{{{N_s}}}{{{N_p}}}\\\frac{9}{{120}} = \frac{{{N_s}}}{{400}}\\{N_s} = 30\end{array}\)

Therefore, Number of turns is \(30\).

Calculating the Input Current  

b)Consider the transformer equation,

\(\begin{array}{c}\frac{{{V_s}}}{{{V_p}}} = \frac{{{I_p}}}{{{I_s}}}\\\frac{9}{{120}} = \frac{{{I_p}}}{{1.30}}\\{I_p} = 9.75 \times {10^{ - 2}}\;A\end{array}\)

Therefore, input current is\(9.75 \times {10^{ - 2}}\;A\).