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The diagram shows a circuit containing a light-dependent resistor (LDR) attached across an ohmmeter - Junior Cycle Science - Question b - 2017

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The diagram shows a circuit containing a light-dependent resistor (LDR) attached across an ohmmeter. Light from a lamp shines directly on the LDR. (i) How could the... show full transcript

Worked Solution & Example Answer:The diagram shows a circuit containing a light-dependent resistor (LDR) attached across an ohmmeter - Junior Cycle Science - Question b - 2017

Step 1

How could the intensity of the light shining on the LDR be changed?

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Answer

The intensity of the light shining on the LDR can be changed by adjusting its distance from the lamp. Specifically, you could:

  • Move the lamp closer to increase light intensity.
  • Move the lamp further away to decrease light intensity.
  • Alternatively, you can reduce the brightness of the lamp or change the bulb to one with a different wattage for an overall change in light output.

Step 2

Using the axes on the right, sketch a graph to show how the resistance of the LDR is affected by light intensity.

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The graph should illustrate an inverse relationship where the resistance of the LDR decreases as the light intensity increases. It begins with high resistance at low intensity and declines sharply as intensity rises.

egin{center} Graph:

Resistance | |
|
|
|
|
| | |____________________________________________________ Light Intensity

ext{

As light intensity increases, resistance decreases. } egin{center}

Step 3

State one use of an LDR.

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Answer

One common use of an LDR is in light sensors for security systems, where it can detect ambient light levels to turn on or off street lighting automatically.

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