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\(1.30{\rm{ }}A\)?

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

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,

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

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 \(30\).

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\(9.75 \times {10^{ - 2}}\;A\).