Transcript L4 – Resistance

Moving
Object
Can you match up
the objects with
the substance that
resists them?
What does
“resist” mean?
Do any of these
resistances
change?
When/Why/How
Resisted By
Boat
Air
Current /
Electrons
Water
Skydiver
Atoms
•The boat is resisted by water
•The Water stops the boat from moving any faster, it
opposes the motion of the boat.
•Would the temperature of the
What If...
water affect the resistance?
The boat was in a
lake made of
treacle?
•Can you explain why using the
particle model?
What If...
The boat was in a lake made of treacle?
Resistance would increase
So the boat would go slower
•Would the temperature of the water affect the
resistance?
•Can you explain why using the particle model?
•Higher temperature
•Particles vibrate more
•Particles collide more and spread out
•Liquid expands and becomes less dense
•Resistance decreases
The skydiver is
resisted by air
Skydiver
What happened
to the resistance
as Felix
Baumgartner fell
closer to earth?
It increased
Air
ELECTRICITY
RESISTANCE
These are the
atoms that
electrons
move through
They cause an
electric
resistance to
current
Different conductors have different:
•Areas and lengths
•Sized atoms
•Spaces between the atoms
•Amounts of electrons
Which gives them different resistances
Definition of resistance
•
•
Resistance is a measure of how hard it is
for a current to flow through a component
in a circuit.
Resistors are added into a circuit to reduce
the amount of current flowing. The bigger
the value of resistance, the lower the
current.
“Different resistances” placemats
Look at the placemats about wires of
Different resistances, and a rheostat set to
different resistances.
Be ready to report back to the class.
Practical
Use test circuit to get results onto
worksheet, then draw graph to find
relationship between voltage and current.
Plenary
 Write a paragraph about the journey of an
electron around a circuit containing a bulb and a
resistor.
 You should write about the energy transfers that
are going on in the circuit.