Light-dependant Resistors

• What is the symbol for a light dependent resistor?

  It is called an LDR
• How does the resistance of an LDR change in light conditions?

  Resistance is low in light and high in dark
• What is the relationship between current and potential difference in an ohmic conductor?

  Current is directly proportional to potential difference
• What happens to the current through a resistor when temperature is constant?

  It remains directly proportional to potential difference
• What is the function of an LDR in circuits?

  To detect light
• How does an LDR function in a mobile phone?

  It turns off the screen when near the ear
• How does the resistance of an LDR change in different light conditions?

  • High resistance in dark conditions
  • Low resistance in light conditions
• What happens to the potential difference across an LDR when it is in darkness?

  The potential difference across the LDR is high
• What is the effect on the lamp when the LDR is in darkness?

  The lamp becomes very dim
• What is the potential difference of the cell in the mobile phone circuit example?

  10 volts
• How do garden lamps utilize LDRs?

  • Light turns on in darkness
  • Light turns off in daylight
• Where can you find more questions about LDRs?

  In the vision workbook
• What is the simplified circuit example involving an LDR and a lamp?

  An LDR in series with a lamp
• How does the potential difference behave in a series circuit with an LDR and a lamp?

  It is shared between the components