Shortcut Methods

Shortcuts and Tricks


1. Resonant Frequency

fr=12πLC

Remember:

  • Resonant frequency is inversely proportional to the square root of both inductance and capacitance.
  • Higher the values of L and C, Lower is the resonant frequency.

2. Time Constant

τ=RC

Remember:

  • Time constant is simply the product of resistance and capacitance.
  • Higher the resistance, higher the time constant.
  • Higher the capacitance, higher the time constant.

3. Initial Current

Iinitial=V0R

Remember:

  • Initial current is the current flowing in the circuit at t=0, and it is determined solely by the voltage source and resistance.
  • The inductance and capacitance have no effect on the initial current.

4. Voltage across Capacitor at t=0

VC(0)=0,

Remember:

  • At t=0, the capacitor is uncharged, so the voltage across it is zero.
  • Current would start flowing through the resistor and charging the capacitor immediately, but the voltage across the capacitor at t=0 is still 0.

5. Energy stored in Inductor at t=0

EL(0)=0

Remember:

  • At t=0, the inductor cannot store any energy because the current through it is still 0.
  • The energy starts getting stored in the inductor as current starts flowing through it, but at t=0, the energy is still zero.