Download - 02 1 Conduction
-
7/31/2019 02 1 Conduction
1/23
Why are frying-pans and woks usuallymade of metals but their handles aremade of plastic?
Warm-up
-
7/31/2019 02 1 Conduction
2/23
How is energy transferred from thecooker to the pan and then to the food?
Introduction
-
7/31/2019 02 1 Conduction
3/23
Energy transfer by conduction
Energy is transferredby conduction
from the cooker,
through the pan,
to the food.
-
7/31/2019 02 1 Conduction
4/23
Studying the heat transferred along a metal rod
What happens to
these drawing pins?
Conduction (video)
copper rod
insulating board
wax
drawing pins
-
7/31/2019 02 1 Conduction
5/23
What kind of rod conducts heat?Feel the ends of therods to find out which
rod feels hot first.
Conduction (video)
very hotwater
glass
wood
iron
copper
-
7/31/2019 02 1 Conduction
6/23
Heat the ends of themetal rods and note
which drawing pin atthe other end falls first.
What kind of rod conducts heat fastest?
Conduction (video)
aluminiumcopper
iron
drawingpins
-
7/31/2019 02 1 Conduction
7/23
Does water conduct heat?
Gently heat the toppart of the water & find
out if the ice melts.
Conduction (video)
water wire gauze
ice
boilingtube
-
7/31/2019 02 1 Conduction
8/23
Does air conduct heat?
Leave the
cardboard for awhile & then
take the
temperaturereadings.
Conduction (video)
thermometer
cardboard tube
heater
-
7/31/2019 02 1 Conduction
9/23
Leave the cardboard fora while & then take the
temperature readings.
Conduction (video)
Does air conduct heat?
-
7/31/2019 02 1 Conduction
10/23
Materials conduct heat at different rates.
Metals (e.g. copper and iron) are good
conductorsof heat.Non-metals (e.g. wood, water and air)are poor conductors (or good insulators).
Energy transfer by conduction
In conduction, heat (energy) is transferred
from the part to the part.
-
7/31/2019 02 1 Conduction
11/23
In conduction, heat is transferred from thehot part to the cold part along an object.Conduction is efficient in conductors but notin insulators.
Energy transfer by conduction
-
7/31/2019 02 1 Conduction
12/23
Does the orientation of the rod matter?
Energy transfer by conduction
-
7/31/2019 02 1 Conduction
13/23
Phoebe heats two metal rods as shown.Which will be heated up first? Why?
Does the orientation of the rod matter?
of them are heatedup at the same rate.
Energy transferred from the
hot end to the cold end byconduction is not affected bythe orientation of the rod.
-
7/31/2019 02 1 Conduction
14/23
Conduction and particle motion
In kinetic theory,
particles at hotend vibrate a lot
particles atcold endvibrate lessparticles in a solid are
closely packed,
they vibrate to & fro butcan't change positions.
-
7/31/2019 02 1 Conduction
15/23
Conduction and particle motion
The fast vibrating particlesbump into the slowerneighbouring particles &
particles at hotend vibrate a lot
particles at
cold endvibrate less
make them vibrate morerapidly
(from one particle to thenext & from hot to coldend of rod)
-
7/31/2019 02 1 Conduction
16/23
Conduction and particle motion
(simulation)
-
7/31/2019 02 1 Conduction
17/23
Examples of conduction
A cotton jacketkeeps warm bytrapping air next tothe body.
-
7/31/2019 02 1 Conduction
18/23
Examples of conduction
Polar bears keepwarm by trappingair in the fur.
-
7/31/2019 02 1 Conduction
19/23
Examples of conduction (video)
Birds keep warmby trapping air in
their feathers.
-
7/31/2019 02 1 Conduction
20/23
Examples of conduction
Under the same condition, a metal blockfeels colder than a wooden block even the 2
objects are at the same temperature.
metal easily conducts energy away fromyour hand
you feel cold
-
7/31/2019 02 1 Conduction
21/23
A From high-temperature area to low-temperature area.
B From low-temperature area to high-temperature area.
C The direction of heat transferred is different inmetals and non-metals.
In conduction, heat is transferred...
In conduction, heat is transferred in which ofthe following direction?
-
7/31/2019 02 1 Conduction
22/23
A The temperature of the tile floor is lower.
B Tile is a better conductor of heat than wood.
C Wood is a better conductor of heat than tile.
D Tile is smoother than wood.
Which of the following can explain why a tilefloor feels colder than a wooden floor?
-
7/31/2019 02 1 Conduction
23/23
Frying-pans are made of...
conductors
Frying-pans are made of metals becausethey are good _________ of heat, whilehandles of frying-pans are made of plasticbecause they are good _________ of heat.insulators