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

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 $10\text{ cm}$.

(a) Calculate the energy stored by a $100\text{-}\mu\text{F}$ capacitor charged to $100\text{ V}$. (b) If this capacitor is now connected across another $100\text{-}\mu\text{F}$ capacitor that is uncharged, calculate the total energy stored by both capacitors. ($\text{}$c) Is the energy stored by both capacitors in part (b) less than the energy stored by the single capacitor in part (a)? If yes, where did the energy go?

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 $R_3$.

How much is the induced voltage, $V_\text{L}$, across a $5\text{-H}$ inductor carrying a steady dc current of $200\text{ mA}$? a. $0\text{ V}$. b. $1\text{ V}$. c. $100\text{ kV}$. d. $120\text{ Vac}$.

Two inductors, $L_1$ and $L_2$, have a coefficient of coupling, $k$, equal to $0.5$. $L_1=100\text{ mH}$ and $L_2=150\text{ mH}$. Calculate $L_\text{M}$.

If an iron-core transformer has a turns ratio, $\dfrac{\text{N}_\text{P}}{\text{N}_\text{S}}$, of $3:1$ and $Z_\text{S}=16\space\Omega$, how much is $Z_\text{P}$? a. $48\space\Omega$. b. $144\space\Omega$. c. $1.78\space\Omega$. d. $288\space\Omega$.

The electrical length of an antenna is to be one-half wavelength long at a frequency $f$ of $7.2\text{ MHz}$. Calculate the length of the antenna in (a) feet; (b) centimeters.

Two $50\text{-mH}$ coils, $L_1$ and $L_2$, have a coefficient of coupling, $k$, equal to $0.6$. Calculate $L_\text{M}$.

A step-down transformer has a turns ratio, $\dfrac{\text{N}_\text{P}}{\text{N}_\text{S}}$, of $4:1$. If the primary voltage, $V_\text{P}$, is $120\text{ Vac}$, how much is the secondary voltage, $V_\text{S}$? a. $480\text{ Vac}$. b. $120\text{ Vac}$. c. $30\text{ Vac}$. d. It cannot be determined.

Ms. Morris will turn 65 on June 10th. She has never previously qualified for Medicare. She is entitled to Medicare Part A and intends to enroll in Part B. She wants to know if she can enroll in a Medicare Advantage plan with prescription drug coverage. What do you tell her?

A coil, $L_1$, produces $40\space\mu\text{Wb}$ of magnetic flux. A coil, $L_2$, nearby, is linked with $L_1$ by $30\space\mu\text{Wb}$ of magnetic flux. What is the value of $k$?

A transmission line has a length $l$ of $7.5\text{ m}$. What is its electrical wavelength at $10\text{ MHz}$?