Graph Interpretation: To identify a component, plot current on the y-axis against voltage on the x-axis. A straight line through the origin identifies a constant resistor, while a curve indicates a variable resistance component.
Diode Identification: Diodes are recognized by a graph that remains at zero for negative voltages (reverse bias) and rises sharply only after a specific positive threshold voltage is reached in forward bias.
Measuring Resistance from Graphs: At any specific point on an IV curve, the resistance can be calculated using the ratio . Note that for non-linear graphs, the gradient is not directly equal to at all points due to the shifting resistance.
Symbol Precision: Always verify the direction of arrows on symbols; arrows pointing towards the component indicate sensitivity to light (LDR), while arrows pointing away indicate light emission (LED).
Logic Checks: When solving circuit problems involving LDRs or thermistors, always perform a 'sanity check': if the temperature goes up, the resistance must go down, causing the circuit current to increase.
Gradient Interpretation: On an graph, a steeper slope indicates lower resistance, while a flatter slope indicates higher resistance. This is a common source of confusion in multiple-choice questions.
Misunderstanding Diode Symbols: Students often forget that the 'triangle' in a diode symbol points in the direction that conventional current is allowed to flow. Connecting it against this direction results in near-infinite resistance.
Filament Lamp Linear Assumption: A common error is assuming filament lamps follow Ohm's Law. They do not; their resistance changes significantly as they glow, making them non-ohmic.
Confusing LDR/Thermistor Trends: Many learners mistakenly believe resistance increases with intensity or temperature. Remember 'LURD': Light Up, Resistance Down (and the same applies to NTC thermistors).
