Named after the English physicist James Prescott Joule, the joule is a unit of energy in the International System of Units. A single joule represents the energy transferred when a force of one newton acts over a meter. To put it in everyday terms, the energy used to lift a small apple one meter off the ground is approximately one joule. Interestingly, the joule is also the energy released in one second by a current of one ampere through a resistance of one ohm, showcasing its versatility across both mechanical and electrical domains.
While joules measure energy, they can also power curiosity. For instance, the daily recommended caloric intake for an average adult translates to roughly 8,700,000 joules. This highlights the joule’s role not only in physics but also in our nutrition and daily energy consumption, offering a glimpse into the complex interplay between energy, food, and our bodies.
The kilojoule, abbreviated as kJ, is a unit of energy in the International System of Units. While it may not be as commonly recognized as calories in everyday conversation, the kilojoule is actually the standard metric unit for quantifying energy. Fascinatingly, 1 kilojoule is equivalent to 0.239 calories, making it a handy unit for converting nutritional information, especially in countries that primarily use the metric system.
Interestingly, the term “joule” is named after the English physicist James Prescott Joule, who studied the nature of heat and discovered its relationship to mechanical work. This unit has applications far beyond nutrition, including physics, chemistry, and engineering, where it measures various types of energy transformations, from kinetic to thermal. Understanding kilojoules can deepen our appreciation of energy, highlighting the intricate balances that power our world and our bodies.
| Joules | Kilojoules |
|---|---|
0
J
|
0
kJ
|
100
J
|
0.1
kJ
|
200
J
|
0.2
kJ
|
300
J
|
0.3
kJ
|
400
J
|
0.4
kJ
|
500
J
|
0.5
kJ
|
600
J
|
0.6
kJ
|
700
J
|
0.7
kJ
|
800
J
|
0.8
kJ
|
900
J
|
0.9
kJ
|
1000
J
|
1
kJ
|
1100
J
|
1.1
kJ
|
1200
J
|
1.2
kJ
|
1300
J
|
1.3
kJ
|
1400
J
|
1.4
kJ
|
1500
J
|
1.5
kJ
|
1600
J
|
1.6
kJ
|
1700
J
|
1.7
kJ
|
1800
J
|
1.8
kJ
|
1900
J
|
1.9
kJ
|
2000
J
|
2
kJ
|
2100
J
|
2.1
kJ
|
2200
J
|
2.2
kJ
|
2300
J
|
2.3
kJ
|
2400
J
|
2.4
kJ
|
2500
J
|
2.5
kJ
|
2600
J
|
2.6
kJ
|
2700
J
|
2.7
kJ
|
2800
J
|
2.8
kJ
|
2900
J
|
2.9
kJ
|
3000
J
|
3
kJ
|
3100
J
|
3.1
kJ
|
3200
J
|
3.2
kJ
|
3300
J
|
3.3
kJ
|
3400
J
|
3.4
kJ
|
3500
J
|
3.5
kJ
|
3600
J
|
3.6
kJ
|
3700
J
|
3.7
kJ
|
3800
J
|
3.8
kJ
|
3900
J
|
3.9
kJ
|
4000
J
|
4
kJ
|
4100
J
|
4.1
kJ
|
4200
J
|
4.2
kJ
|
4300
J
|
4.3
kJ
|
4400
J
|
4.4
kJ
|
4500
J
|
4.5
kJ
|
4600
J
|
4.6
kJ
|
4700
J
|
4.7
kJ
|
4800
J
|
4.8
kJ
|
4900
J
|
4.9
kJ
|
5000
J
|
5
kJ
|
5100
J
|
5.1
kJ
|
5200
J
|
5.2
kJ
|
5300
J
|
5.3
kJ
|
5400
J
|
5.4
kJ
|
5500
J
|
5.5
kJ
|
5600
J
|
5.6
kJ
|
5700
J
|
5.7
kJ
|
5800
J
|
5.8
kJ
|
5900
J
|
5.9
kJ
|
6000
J
|
6
kJ
|
6100
J
|
6.1
kJ
|
6200
J
|
6.2
kJ
|
6300
J
|
6.3
kJ
|
6400
J
|
6.4
kJ
|
6500
J
|
6.5
kJ
|
6600
J
|
6.6
kJ
|
6700
J
|
6.7
kJ
|
6800
J
|
6.8
kJ
|
6900
J
|
6.9
kJ
|
7000
J
|
7
kJ
|
7100
J
|
7.1
kJ
|
7200
J
|
7.2
kJ
|
7300
J
|
7.3
kJ
|
7400
J
|
7.4
kJ
|
7500
J
|
7.5
kJ
|
7600
J
|
7.6
kJ
|
7700
J
|
7.7
kJ
|
7800
J
|
7.8
kJ
|
7900
J
|
7.9
kJ
|
8000
J
|
8
kJ
|
8100
J
|
8.1
kJ
|
8200
J
|
8.2
kJ
|
8300
J
|
8.3
kJ
|
8400
J
|
8.4
kJ
|
8500
J
|
8.5
kJ
|
8600
J
|
8.6
kJ
|
8700
J
|
8.7
kJ
|
8800
J
|
8.8
kJ
|
8900
J
|
8.9
kJ
|
9000
J
|
9
kJ
|
9100
J
|
9.1
kJ
|
9200
J
|
9.2
kJ
|
9300
J
|
9.3
kJ
|
9400
J
|
9.4
kJ
|
9500
J
|
9.5
kJ
|
9600
J
|
9.6
kJ
|
9700
J
|
9.7
kJ
|
9800
J
|
9.8
kJ
|
9900
J
|
9.9
kJ
|
10000
J
|
10
kJ
|
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