Theory of Electricity
Review these from S1.
- Charge
- Potential difference
- Current
- Power
- Kirchoff’s laws
- Circuit elements
- Resistors
- Capacitors - Voltage through a capacitor cannot change instantaneously
- Inductors- Current through an inductor cannot change instantaneously
- Impedance & Admittance
- Active elements
- AC Theory
Types of active elements
| Source | Notation |
|---|---|
| Current Source | |
| DC Voltage Source | |
| AC Voltage Source |
Independent source
The terminal voltage or current depends only on the loading & internal source quantity.
Dependent source
The terminal voltage or current depends on another circuit quantity such as a voltage or current. Categorized into 4.
- Voltage-controlled voltage source
- Voltage-controlled current source
- Current-controlled voltage source
- Current-controlled current source
Dependent sources are denoted with the relationship with another independent source.
Waveform errors
DC Offset
A DC voltage superimposed on a AC waveform shifts it up or down. Causes unwanted clipping of the AC voltage when amplification. Causes the waveform to have reduced dynamic range, reduced headroom, increases noise when amplified and causes problems with DC-coupled circuits.
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Dynamic Range: Refers to the ratio between the largest and smallest signal levels it can handle effectively. Expressed in decibels (dB).
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Headroom: Difference between the nominal operating level of a system and its maximum level before distortion occurs. It provides a safety margin to accommodate unexpected peaks in the signal without causing clipping or distortion. Adequate headroom ensures the integrity of the signal during amplification or processing.
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Nominal Operating Level: Refers to the standard or reference level at which a system is designed to operate optimally.
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Noise: Refers to any unwanted electrical signals or disturbances that interfere with the desired signal. It can be from thermal noise, electromagnetic interference, or circuit imperfections. Reduces the clarity and quality of the signal.
Moving iron instrument
Can be identified by AC symbol. Measures the rms value of the signal.
Moving coil instrument
Can be identified by DC symbol. Measures the average value of the signal.
Moving coil rectifier instrument
Can be identified by diode symbol. Measures the rms value of the rectified signal. Full wave rectifier bridge of 4 diodes is used. Assuming the current is sinusoidal, the scale of this instrument must be marked in terms of 1.11 times the current.