Understanding Dependent Sources in Electrical Networks

In electrical network analysis, sources provide energy or signals to the circuit. These sources can be classified based on how their output quantity (voltage or current) is determined. The question asks about a source whose output is controlled by another voltage or current elsewhere in the circuit.

What is a Dependent Source?

A dependent source is an electrical source whose voltage or current output depends on a voltage or current at a different location within the same circuit. These sources are often used in circuit models for active components like transistors or operational amplifiers.

There are four types of dependent sources:

• Voltage-Controlled Voltage Source (VCVS): The output voltage is proportional to a voltage elsewhere in the circuit.
• Current-Controlled Voltage Source (CCVS): The output voltage is proportional to a current elsewhere in the circuit.
• Voltage-Controlled Current Source (VCCS): The output current is proportional to a voltage elsewhere in the circuit.
• Current-Controlled Current Source (CCCS): The output current is proportional to a current elsewhere in the circuit.

Dependent sources are represented graphically by diamond shapes.

Contrast with Independent Sources

An independent source, on the other hand, provides a voltage or current that is completely independent of other voltages or currents in the circuit. Its output is a constant value or varies with time in a way that is not influenced by the circuit's response (e.g., a standard DC voltage source or AC voltage source). Independent sources are typically represented by circles.

Why Other Options Are Incorrect

• Non-ideal source: This term refers to sources that have internal resistance or impedance, meaning their output voltage or current changes slightly based on the load. While practical sources are non-ideal, this doesn't define whether their output is controlled by another part of the circuit.
• Ideal source: An ideal source is a theoretical concept with perfect characteristics (zero internal resistance for a voltage source, infinite internal resistance for a current source). This describes the source's internal behavior, not its dependency on other circuit quantities.
• Independent source: As explained above, an independent source's output is not controlled by other voltages or currents in the circuit, which is the opposite of the source described in the question.

Therefore, a source whose quantity is controlled by another voltage or current in the circuit is correctly called a dependent source.