2. Current, resistance and potential difference

Available for over a year

Ellie Hurer and James Stewart explore current, resistance and potential difference. They also discuss the relationship between current and resistance in different components. Suitable for: AQA, Edexcel, OCR. For more information on current, resistance and potential difference, check out the BBC Bitesize website: https://www.bbc.co.uk/bitesize/guides/zgvq4qt/revision/3 Key learning objectives discussed in this episode: - The current (I) through a component depends on both the resistance (R) of the component and the potential difference (V) across the component. The greater the resistance of the component the smaller the current for a given potential difference (pd) across the component. - Questions will be set using the term potential difference. Students will gain credit for the correct use of either potential difference or voltage. - Current, potential difference or resistance can be calculated using the equation: - potential difference = current × resistance - Students should be able to explain that, for some resistors, the value of R remains constant but that in others it can change as the current changes. - The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes. - The resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component. - The resistance of a filament lamp increases as the temperature of the filament increases. - The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction. - The resistance of a thermistor decreases as the temperature increases. - The applications of thermistors in circuits eg a thermostat is required. - The resistance of an LDR decreases as light intensity increases. - The application of LDRs in circuits eg switching lights on when it gets dark is required. Students should be able to: - explain the design and use of a circuit to measure the resistance of a component by measuring the current through, and potential difference across, the component - draw an appropriate circuit diagram using the correct circuit symbols. - use graphs to explore whether circuit elements are linear or non-linear and relate the curves produced to their function and properties.