How Current Changes with Voltage for a Component

How Current Changes with Voltage for a Component

  • Current and voltage are closely related in an electric circuit. This relationship is typically described by Ohm’s Law which states that the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance.

  • In simpler terms, if voltage increases in a circuit with constant resistance, the current will also increase. Similarly, if the voltage decreases with constant resistance, the current will decrease. This is under the assumption that the material follows Ohm’s law.

  • For a fixed voltage, the current can be increased by decreasing the resistance in the circuit. Conversely, for a fixed voltage, increasing the resistance will decrease the current. This relationship is the inverse of the voltage-current relation.

  • Not all components in a circuit follow Ohm’s Law though. For components like diodes and thermistors (variable resistors), their resistance varies with current and/or voltage.

  • A diode, for example, allows current to flow easily in one direction but not the other. Hence, the current-voltage relationship for a diode is non-linear i.e., current does not increase proportionally with voltage.

  • A thermistor’s resistance is dependent on temperature. In a hot condition, thermistors have low resistance allowing more current to flow; whereas in a cold condition, the resistance is high hence restricting the flow of current.

  • It is important to understand that the relationship between voltage and current is affected by the type of component used in the circuit, the temperature, and any potential damage to the component, among other factors.

  • Understanding these different relationships between current, voltage and resistance will help in interpreting and predicting the behaviour of electric circuits in various conditions. Remember, voltage is the driving force in a circuit, whereas current is the effect or result of that force.

  • When drawing voltage-current graphs for different components, remember that a resistor has a linear graph, a filament lamp has an S-shape graph (resistance increases with temperature), and a diode has a graph that’s flat for negative voltages and steeply rises for positive voltages (showing that current can only flow in one direction).

  • Recall the phrases ‘directly proportional’ and ‘inversely proportional’. If one thing gets bigger as another gets smaller, they’re inversely proportional. If they both get bigger together, they’re directly proportional.

  • When carrying out practical experiments on how current changes with voltage, it is essential to control variables such as the temperature to ensure accurate results during measurements.