Define a Thermistor and its typical behavior.

A thermistor is a temperature-dependent resistor. For a standard NTC thermistor, the resistance decreases as the temperature of the component increases.

What is the primary difference between an Ohmic and a non-Ohmic conductor?

An Ohmic conductor has a constant resistance, resulting in a linear I-V graph where current is directly proportional to voltage. A non-Ohmic conductor has a resistance that changes with current or environment, resulting in a curved I-V graph.

How does the resistance of an LDR change as light intensity decreases?

As light intensity decreases, the resistance of an LDR increases. This property allows it to be used in circuits that trigger actions in the dark, such as turning on night lights.

Compare the I-V characteristics of a filament lamp and a fixed resistor.

A fixed resistor produces a straight line through the origin, indicating constant resistance. A filament lamp produces an S-shaped curve because its resistance increases as the filament gets hotter, reducing the rate at which current increases at higher voltages.

What is a common mistake when interpreting the gradient of an I-V graph?

A common error is assuming the gradient is the resistance. In an I-V graph (Current vs. Voltage), the gradient is actually the reciprocal of resistance ($\frac{1}{R}$), meaning a steeper line indicates lower resistance.

What happens if a diode is placed in a circuit in 'reverse bias'?

In reverse bias, the diode offers extremely high resistance, preventing current from flowing through that part of the circuit. This is often used for circuit protection.

Why might a student incorrectly conclude a resistor is non-Ohmic during an experiment?

If the student allows the resistor to heat up significantly by using high currents, the resistance will increase. This makes the I-V graph curve, even though the component is intended to be Ohmic under constant conditions.

What is the function of a Variable Resistor (Rheostat)?

A variable resistor allows the user to manually adjust the resistance in a circuit. This is used to control the amount of current flowing, such as in a dimmer switch or volume control.

What is the circuit symbol for an LED?

The symbol for an LED is a standard diode symbol (a triangle pointing to a vertical line) with two small arrows pointing away from it, representing the emission of light.

Explain why the resistance of a filament lamp increases with voltage.

As voltage increases, more current flows, causing more collisions between electrons and metal ions in the filament. these collisions generate heat, which increases the vibrations of the ions, making it harder for electrons to pass through.

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10. Electricity & Circuits

Electrical Components

Summary

Electrical components are the building blocks of circuits, each possessing unique current-voltage (I-V) characteristics that determine how they regulate the flow of charge. Understanding these components involves distinguishing between Ohmic conductors, where resistance remains constant, and non-Ohmic components, where resistance varies based on external factors like temperature, light, or voltage polarity.

1. Definition & Core Concepts

Electrical Components are discrete devices within a circuit that perform specific functions, such as limiting current, storing energy, or converting electrical energy into other forms.
Resistance ( $R$ ) is the measure of a component's opposition to current flow, defined by the ratio of potential difference ( $V$ ) to current ( $I$ ), expressed as $R = \frac{V}{I}$ .
I-V Characteristics refer to the relationship between the current flowing through a component and the potential difference across it, typically represented on a graph with current on the y-axis and voltage on the x-axis.

2. Ohmic vs. Non-Ohmic Conductors

I-V characteristic curves for a fixed resistor (linear) and a filament lamp (S-curve).

3. Sensory Resistors: LDRs and Thermistors

4. Diodes and Directional Flow

5. Key Distinctions

6. Exam Strategy & Tips