# Why voltage amplified

Discussion in 'General Electronics Chat' started by shaam, Nov 4, 2007.

1. ### shaam Thread Starter New Member

Nov 4, 2007
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Why voltage is amplified in the series RLC circuit?who is influencing the voltage,probably that is L or C but how & why does it amplify?

2. ### chesart1 Senior Member

Jan 23, 2006
269
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Energy is stored in a magnetic field in an inductor. The inductor opposes a change in current. The voltage across an inductor is proportional to the rate of change of current. When the current changes, the magnetic field around each loop of the coil changes. While changing, it cuts across the adjacent loop inducing an opposing current. The induced current opposes the changing current.

The formula for the inductor is: the instantaneous voltage across the inductor is equal to the value of the inductor in henries times the rate of change in current. Hence, if a one henry inductor sees a current change of 5 amps in 1 second, a voltage of 5 volts will appear across the inductor.

Energy is stored in an electric field in a capacitor. The formula for a capacitor is.
The instantaneous current through a capacitor is equal to the capacitance in farads times the rate of change of voltage.

The reason for the amplification is that the formulae involve a rate of change and not a magnitude.

3. ### GS3 Senior Member

Sep 21, 2007
408
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Although technically accurate, I think "amplified" can be misleading because when we talk of an "amplifier" we are referring to a power amplifier. A transformer can "amplify" voltages or currents but we do not call it an "amplifier". There is no "amplification" in an RLC circuit in the common acception of the word.

But, if we accept this use of "amplify" it is not difficult to see why resonance leads to "amplification". The resonant components store and return energy. Just like a pendulum clock. Very small impulses at the escape mechanism result in a rather larger swing of the pendulum.