In the circuit shown below, the switch is closed at t = 0. The value o...
To determine the value of θ that will give the maximum value of DC offset of the current at the time of switching, we need to analyze the circuit and calculate the current through it.
1. **Circuit Analysis:**
- Given: R = 3.77 Ω, L = 10 mH, v(t) = 150 sin (377t + θ)
- The circuit consists of a resistor (R) and an inductor (L) connected in series.
- When the switch is closed at t = 0, the circuit becomes a DC circuit.
- The current through the circuit can be calculated using Ohm's Law and the properties of inductors.
2. **Calculating the DC Offset:**
- At DC, inductors behave like short circuits, and the current through them is constant.
- Therefore, the inductor can be replaced with a short circuit.
- The circuit now consists of a resistor (R) connected directly to the voltage source (v(t)).
- The current through the circuit can be calculated using Ohm's Law: I = V/R, where V is the voltage across the resistor.
- The voltage across the resistor is given by V = v(t) - V_offset, where V_offset is the DC offset of the voltage waveform.
- To find the maximum value of the DC offset, we need to find the maximum value of V_offset.
3. **Calculating the Maximum DC Offset:**
- The maximum value of V_offset occurs when the voltage waveform v(t) is at its peak.
- At the peak of a sine wave, the phase angle θ is either 90° or -90°.
- Plugging in θ = 90° into the voltage waveform equation, we get v(t) = 150 sin (377t + 90°).
- The maximum value of V_offset can be calculated by finding the difference between the peak value of v(t) and the average value of the waveform.
- The average value of a sine wave over one period is zero.
- Therefore, the maximum value of V_offset is equal to the peak value of v(t) when θ = 90°.
- Plugging in θ = 90° into the voltage waveform equation, we get v(t) = 150 sin (377t + 90°) = 150.
- Hence, the maximum value of the DC offset is 150V.
4. **Conclusion:**
- The value of θ in degrees that will give the maximum value of DC offset of the current at the time of switching is 90°.
- Therefore, the correct answer is option (C) 90.