Calculate the inductive reactance, $X_\text{L}$, of a $50\text{-}\mu\text{H}$ coil at the following frequencies: a. $f=60\text{ Hz}$. b. $f=10\text{ kHz}$. c. $f=500\text{ kHz}$. d. $f=3.8\text{ MHz}$.

Using your answer from Prob. 19–37, calculate a. the primary impedance, $Z_\text{P}$. b. the power delivered to the $4\text{-}\Omega$ speaker. c. the primary power.

State what two kinds of questions that you should avoid during an interview.

Explain the advantages of a transformer having an isolated secondary.

In Fig. 19–38, what turns ratio, $\dfrac{\text{N}_\text{P}}{\text{N}_\text{s}}$, is required to obtain a secondary voltage of a. $60\text{ Vac}$? b. $600\text{ Vac}$? c. $420\text{ Vac}$? d. $24\text{ Vac}$? e. $12.6\text{ Vac}$?

In Fig. 19–36, calculate the primary current, $I_\text{P}$, if $R_{\text{L}_1}$ opens.

What is the assumed value of $k$ for an iron-core transformer?

Repeat Prob. 19–19 if $N_\text{P}:N_\text{S}=10:1$.

Two coils are mutually coupled, with L1=50 mH, L2=120 mH, and k=0.5. Calculate the maximum possible equivalent inductance if the coils are connected in parallel

A coil, $L_1$, produces $200\space\mu\text{Wb}$ of magnetic flux. A nearby coil, $L_2$, is linked with $L_1$ by $50\space\mu\text{Wb}$ of magnetic flux. What is the coefficient of coupling, $k$, between $L_1$ and $L_2$?

How much is the self-induced voltage across a $33\text{-mH}$ inductance when the current changes at the rate of $1500\space\frac{\text{A}}{\text{s}}$?

Calculate the inductance, $L$, for the following long coils: (Note: $1\text{ m}=100\text{ cm}$ and $1\text{ m}^2=10,000\text{ cm}^2$.) a. air core, $20$ turns, area $3.14\text{ cm}^2$, length $25\text{ cm}$. b. same coil as step a with ferrite core having a $\mu_\text{r}$ of $5000$. c. air core, $200$ turns, area $3.14\text{ cm}^2$, length $25\text{ cm}$. d. air core, $20$ turns, area $3.14\text{ cm}^2$, length $50\text{ cm}$. e. iron core with $\mu_\text{r}$ of $2000$, $100$ turns, area $5\text{ cm}^2$, length $10\text{ cm}$.

What value of inductance will provide an $X_\text{L}$ of $500\space\Omega$ at a frequency of $159.15\text{ kHz}$? a. $5\text{ H}$. b. $500\space\mu\text{H}$. c. $500\space\text{mH}$. d. $750\space\mu\text{H}$.

If the bleeder current, $I_\text{B}$, is $15\text{ mA}$ in Fig. 7–32, solve for a. $I_1$, $I_2$, $I_3$, and $I_\text{T}$. b. $V_1$, $V_2$, and $V_3$. c. $R_1$, $R_2$, and $R_3$. d. The power dissipated by $R_1$, $R_2$, and $R_3$.