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

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

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

5. Diode Is the diode an Ohmic conductor? No, because the I – V graph is not a straight line, i.e. I is not directly proportional to V. V 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. Point on the V axis the voltage at which the current starts increasing. 0.6 V is the voltage at which the diode starts working, i.e. current flows through it. This voltage is called Activation Voltage. 0.6 V

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

7. Light Dependent Resistor LDR The resistance in LDRs depends on how much light shines on them. Light intensity Resistance ( Ω ) Choose the right ending. As the light increases… 1. the current decreases.the current decreases. 2. the current stays the same.the current stays the same. 3. the current increases.the current increases. DarkBright

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

11. Thermistor (Temperature Dependent Resistor) The resistance in thermistors depends on the temperature. Temperature Resistance ( Ω ) CoolHot Choose the right ending. As it gets cooler… 1. the current decreases.the current decreases. 2. the current stays the same.the current stays the same. 3. the current increases.the current increases.

14. Cell or Battery Resistor LDR Diode Thermistor Filament lamp

15. Cell or Battery Resistor LDR Diode Thermistor Filament lamp