To address the tasks involving the given circuit in your images, let's go step by step. The circuit consists of a resistor $R$, inductor $L$, and capacitor $C$ in series with an AC voltage source $V_s$.

Given data:

• Voltage source $V_s = 10 \, V$
• Frequency $f = 1.5 \, kHz$
• $R = 15 \, \Omega$
• $L = 2.7 \, mH$
• $C = 1.8 \, \mu F$

Part (a): Frequency for Resonance

For resonance in an RLC series circuit, the frequency $f_r$ is given by the following formula:

$f_r = \frac{1}{2 \pi \sqrt{LC}}$

Where:

• $L$ is inductance in Henrys (H),
• $C$ is capacitance in Farads (F).

First, let's convert the values of $L$ and $C$ to standard units:

• $L = 2.7 \, mH = 2.7 \times 10^{-3} \, H$
• $C = 1.8 \, \mu F = 1.8 \times 10^{-6} \, F$

Now, we can calculate the resonant frequency $f_r$.

Part (b): Current at Resonance

Once the circuit is at resonance, the impedance $Z$ of the circuit is at a minimum. At resonance, the impedance is equal to the resistance $R$. The current $I$ drawn from the voltage source can be calculated using Ohm's law:

$I = \frac{V_s}{R}$

Where:

• $V_s = 10 \, V$,
• $R = 15 \, \Omega$.

Part (c): What Happens if the Source is Changed from AC to DC

If the source is switched from AC to DC, the behavior of the circuit changes. For DC:

• The inductor initially resists changes in current but eventually behaves like a short circuit once the current becomes constant.
• The capacitor will behave as an open circuit after being fully charged, blocking any DC current.

Thus, after a brief period, no current would flow in the circuit under DC conditions, assuming ideal components.

Part (d): Resonance Curve Simulation

To produce a resonance curve using a simulator like MicroCap, you would vary the frequency of the voltage source between 800 Hz and 4.5 kHz. The resulting curve would show how the impedance or current changes as the frequency approaches resonance, peaking at the resonant frequency.

Would you like me to proceed with the calculations for parts (a) and (b)? Let me know if you'd like any further details or explanations!