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Understanding Current-Voltage Relationships in Circuit Components

Learn about the relationship between current and voltage in resistors, LDRs, thermistors, diodes, and filament lamps through graphs and resistance dependencies. Discover how resistance varies with heat and light intensity for different components.

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Understanding Current-Voltage Relationships in Circuit Components

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  1. How hot is it? • Current – Voltage graphs • Dependence of resistance on heat • LDRs and thermistors

  2. Current – Voltage graphs A resistor at constant temperature What is the component represented by this graph? The gradient of the line is I/V, but R = V/I  gradient = 1/R Lower resistance I Draw another line for a resistor with lower resistance Draw another line for a resistor with higher resistance Higher resistance V The current through a resistor (at constant temperature) is directly proportional to the voltage. The steeper the gradient, the lower the resistance

  3. Filament lamp No, because the I – V graph is not a straight line, i.e. I is not directly proportional to V. Is the filament lamp an Ohmic conductor? I The resistance of the metal filament inside the bulb increases as the filament gets hotter Hot Cool V As more current flows, the metal filament gets hotter, so its resistance increases. That’s why the graph gets flatter. Write on your graph “hot” and “cool” in the regions where the filament is hotter and cooler and explain why. Hot

  4. Diode No, because the I – V graph is not a straight line, i.e. I is not directly proportional to V. Is the diode an Ohmic conductor? I There is current flowing only when the voltage is positive. This means that almost no current flows if the voltage is applied in the reverse direction. V 0.6 V 0.6 V is the voltage at which the diode starts working, i.e. current flows through it. This voltage is called Activation Voltage. Point on the V axis the voltage at which the current starts increasing.

  5. Light Dependent Resistor LDR The resistance in LDRs depends on how much light shines on them. When is the resistance higher? Resistance (Ω) When it is darker! When is the resistance lower? When it is brighter! Write on the light intensity axis bright and dark in the appropriate places. Dark Bright Light intensity

  6. Light Dependent Resistor LDR The resistance in LDRs depends on how much light shines on them. Choose the right ending. As the light increases… Resistance (Ω) • the current decreases. • the current stays the same. • the current increases. Dark Bright Light intensity

  7. Wrong. Try again

  8. This is the right answer

  9. Thermistor (Temperature Dependent Resistor) The resistance in thermistors depends on the temperature. In what conditions is the resistance higher? Resistance (Ω) In cool conditions! In what conditions is the resistance lower? In hot conditions! Write on the temperature axis hot and cool in the appropriate places. Cool Hot Temperature

  10. Thermistor (Temperature Dependent Resistor) The resistance in thermistors depends on the temperature. Resistance (Ω) Choose the right ending. As it gets cooler… • the current decreases. • the current stays the same. • the current increases. Cool Hot Temperature

  11. Wrong. Try again

  12. This is the right answer

  13. Circuit Components Cell or Battery Resistor Thermistor Diode Filament lamp LDR

  14. Circuit Components Cell or Battery Resistor Thermistor Diode Filament lamp LDR

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