Transcript Static Charge to Electric Current - science

21 July 2015
LDRs and ThermistorsI
Objectives
Be able to describe how the resistance of LDRs and
Thermistors varies.
HSW: AF4 – Using investigative approaches
Used before in: lesson 7 - Diodes
Will use again in:
PLTS: Team workers – Work collaboratively with others.
Used before in: lesson 7 - Diodes
Will use again in:
Keywords
Current (I), Amp, Voltage (V), Volts, ammeter, voltmeter, resistor, thermistor, LDR, resistance (R), Ohm.
Draw the symbols – which is which?
LDR
Thermistor
OUTCOMES
• All students should be able to describe that not
all components conduct electricity by Ohm’s Law.
• Most students should be able to describe the
shape of Resistance-Light Intensity Graph for an
LDR and Resistance-Temperature Graph for a
Thermistor.
• Some students should be able to explain that
semiconductor components use energy to release
electrons and that this reduces resistance.
• Student Model thermistors and LDRs
• What happens to atoms when the amount
of energy increases?
• What happens to electrons as the amount
of energy increases?
• What happens to the resistance as the
amount of energy increases?
Current-Potential Graph of a
filament bulb
• Set up the equipment as shown:
Results
Independent
variable
(temperature or
Light intensity)
• Follow the instructions on the sheet
and take readings of resistance.
• Analysis
• Once you have a set of results draw
a graph of Resistance on the y-axis
and your independent variable on
the x-axis and write a conclusion.
Resistance
(Ω)
Two simple components:
1) Light dependant resistor –
resistance DECREASES when light
intensity INCREASES
Resistance
21/07/2015
2) Thermistor – resistance
DECREASES when temperature
INCREASES
Resistance
Amount of light
Temperature
Electrical Taboo
• Can you describe all the circuit symbols without
saying the words on the cards?