Difference between revisions of "Light Dependent Resistor"

Revision as of 20:24, 27 February 2019

Key Stage 4

Meaning

The symbol for a light dependent resistor.

A light dependent resistor (LDR) is a resistor which changes resistance depending on the intensity of light that it is exposed to.

About Light Dependent Resistors

Light dependent resistors decrease resistance as the intensity of light increases.

A light dependent resistor can be used to control the current passing through a circuit. If the potential difference is constant then the current decreases as the light intensity decreases.

A light dependent resistor can be used to control the potential difference of another component in series with it. If the light intensity on the light dependent resistor is decreased then the potential difference across other components will decrease.

Light dependent resistors can be used in security lights and street lamps which activate depending on how dark it is.


In this circuit diagram the light intensity is low, which causes the resistance of the LDR to be high. As a result the potential difference across the lamp will be high (5.9V) and the current through the lamp will be large. So in dim light the lamp will remain unlit.	In this circuit diagram the light intensity is high, which causes the resistance of the LDR to be low. As a result the potential difference across the lamp will be low (0.1V) and the current through the lamp will be low. So in bright light the lamp will remain unlit.

@@ Line 2: / Line 2: @@
 ===Meaning===
 [[File:LightDependentResistorSymbol.png|right|300px|thumb|The symbol for a '''light dependent resistor'''.]]
-A '''light dependent resistor''' is a [[resistor]] which changes [[Electrical Resistance|resistance]] depending on the intensity of [[light]] that it is exposed to.
+A '''light dependent resistor''' ('''LDR''') is a [[resistor]] which changes [[Electrical Resistance|resistance]] depending on the intensity of [[light]] that it is exposed to.
 ===About Light Dependent Resistors===
@@ Line 9: / Line 9: @@
 : A '''light dependent resistor''' can be used to control the [[Potential Difference|potential difference]] of another [[Electrical Component|component]] in [[Series Circuit|series]] with it. If the [[light]] intensity on the '''light dependent resistor''' is decreased then the [[Potential Difference|potential difference]] across other [[Electrical Component|components]] will decrease.
 : '''Light dependent resistors''' can be used in security [[light]]s and street lamps which activate depending on how dark it is.
+{| class="wikitable"
+|-
+|[[File:LDRPotentialDivider1.png|center|300px]]
+|[[File:LDRPotentialDivider2.png|center|300px]]
+|-
+| style="height:20px; width:200px; text-align:center;" |In this [[Circuit Diagram|circuit diagram]] the [[light]] intensity is low, which causes the [[Electrical Resistance|resistance]] of the '''LDR''' to be high. As a result the [[Potential Difference|potential difference]] across the [[electrical bulb|lamp]] will be high (5.9V) and the [[Electrical Current|current]] through the [[Electrical Bulb|lamp]] will be large. So in dim [[light]] the [[Electrical Bulb|lamp]] will remain unlit.
+| style="height:20px; width:200px; text-align:center;" |In this [[Circuit Diagram|circuit diagram]] the [[light]] intensity is high, which causes the [[Electrical Resistance|resistance]] of the '''LDR''' to be low. As a [[result]] the [[Potential Difference|potential difference]] across the [[electrical bulb|lamp]] will be low (0.1V) and the [[Electrical Current|current]] through the [[Electrical Bulb|lamp]] will be low. So in bright [[light]] the [[Electrical Bulb|lamp]] will remain unlit.
+|}