A model-train transformer plugs into $120~\mathrm{V}$ ac and draws $0.35$ A while supplying $6.8 \mathrm{~A}$ to the train. Is the transformer step-up or step-down?

While demonstrating Faraday's law to her class, a physics professor inadvertently moves the gold ring on her finger from a location where a $0.68 \mathrm{~T}$ magnetic field points along her finger to a zero-field location in $45 \mathrm{~ms}$. The $1.5 \mathrm{~cm}$ diameter ring has a resistance and mass of $55 \mu \Omega$ and $15 \mathrm{~g}$, respectively. Estimate the thermal energy produced in the ring due to the flow of induced current.

Is the ac current in the inductor always the same as the current in the resistor of an $L R C$ circuit? Explain.

A step-up transformer increases 25 V to 120 V. What is the current in the secondary coil as compared to the primary coil?

A transformer has $360$ turns in the primary coil and $120$ in the secondary coil. What kind of transformer is this, and by what factor does it change the voltage? By what factor does it change the current? Assume $100 \%$ efficiency.

An LRC resonant circuit is often called an oscillator circuit. What is it that oscillates?

Describe how to make the impedance in an LRC circuit a minimum.

A transformer is designed to change $117 \mathrm{~V}$ into $13,500 \mathrm{~V}$, and there are $148$ turns in the primary coil. How many turns are in the secondary coil? Assume $100 \%$ efficiency.

Describe briefly how the frequency of the source emf affects the impedance of an LRC circuit far from resonance (R small).

Describe briefly how the frequency of the source emf affects the impedance of an LRC circuit near resonance (R small).

Describe briefly how the frequency of the source emf affects the impedance of a pure inductance.

Describe briefly how the frequency of the source emf affects the impedance of a pure capacitance.

Describe briefly how the frequency of the source emf affects the impedance of a pure resistance.

In an LRC circuit, can the rms voltage across a capacitor, be greater than the rms voltage of the ac source? Explain.