What are these objects?

Order them from coldest to hottest

What are these objects?

Order them from coldest to hottest

kT is about how much energy

particles have at temperature T in

kelvin

Worked example

• On a nice summer’s day (27 oC) how much energy would the particles have?

Worked answer

JkT

KJKkTQ

JKk

KCT o

21

123

123

101.4

3001038.1

1038.1

30027

Example questions

• Determine the amount of energy a particle would have if it were:

– In the centre of the Sun– In the centre of a supernova– In Mars’ northern polar cap– In interstellar space

Location k / JK-1 T / K kT / J

Centre of the Sun 1.38 x 10-23

Centre of a supernova 1.38 x 10-23

Within magma 1.38 x 10-23

Within Mars' northern polar cap

1.38 x 10-23

In interstellar space 1.38 x 10-23

Location k / JK-1 T / K kT / J

Centre of the Sun 1.38E-23 1.50E+07 2.07E-16

Centre of a supernova 1.38E-23 1.00E+11 1.38E-12

Within magma 1.38E-23 1.00E+03 1.38E-20

Within Mars' northern polar cap

1.38E-23 2.30E+02 3.17E-21

In interstellar space 1.38E-23 3.00E+00 4.14E-23

If T = 10 000 K

eVkT 1

The eV

• The energy gained by an electron as it moves through a potential difference of 1 V

JW

VCW

QVW

Q

WV

19

19

106.1

1106.1

Show kT = 1eV (T = 10000K)

eVkT

JeV

JkT

KkT

KT

1

106.11

1038.1

100001038.1

10000

19

19

24

Ideal gaskT

2

1

kT2

1

kT2

3 kT2

1

kT2

1

kT2

1

kT2

1

kT3

Hotter and hotter

Life at T = 300 K

Fires and kilns, T = 1500 K

White hot at the Sun’s surface, T = 6000 K

Hotter still: inside the Sun, T = 6000000 K