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.
The watt-second is a unit of energy that represents the amount of work done when a power of one watt is sustained for one second. This unit is a direct way to visualize energy transfer in everyday activities. Interestingly, while it may sound abstract, this unit can be directly applied to understand how quick appliances like LED lights or small electronic devices consume energy. For example, a modern LED bulb that consumes 10 watts of power will use 10 watt-seconds of energy every second it is on.
While commonly overshadowed by the more familiar joule, the watt-second is essentially equivalent to one joule. Its simplicity in denoting power over time makes it a cornerstone concept in physics and engineering, where it is applied to calculate specific energy transfers and efficiency in varied systems. Exploring this unit helps bridge the gap between theoretical energy calculations and practical everyday energy use.
Kilojoules | Watt-seconds |
---|---|
0
kJ
|
0
Ws
|
10
kJ
|
10000
Ws
|
20
kJ
|
20000
Ws
|
30
kJ
|
30000
Ws
|
40
kJ
|
40000
Ws
|
50
kJ
|
50000
Ws
|
60
kJ
|
60000
Ws
|
70
kJ
|
70000
Ws
|
80
kJ
|
80000
Ws
|
90
kJ
|
90000
Ws
|
100
kJ
|
100000
Ws
|
110
kJ
|
110000
Ws
|
120
kJ
|
120000
Ws
|
130
kJ
|
130000
Ws
|
140
kJ
|
140000
Ws
|
150
kJ
|
150000
Ws
|
160
kJ
|
160000
Ws
|
170
kJ
|
170000
Ws
|
180
kJ
|
180000
Ws
|
190
kJ
|
190000
Ws
|
200
kJ
|
200000
Ws
|
210
kJ
|
210000
Ws
|
220
kJ
|
220000
Ws
|
230
kJ
|
230000
Ws
|
240
kJ
|
240000
Ws
|
250
kJ
|
250000
Ws
|
260
kJ
|
260000
Ws
|
270
kJ
|
270000
Ws
|
280
kJ
|
280000
Ws
|
290
kJ
|
290000
Ws
|
300
kJ
|
300000
Ws
|
310
kJ
|
310000
Ws
|
320
kJ
|
320000
Ws
|
330
kJ
|
330000
Ws
|
340
kJ
|
340000
Ws
|
350
kJ
|
350000
Ws
|
360
kJ
|
360000
Ws
|
370
kJ
|
370000
Ws
|
380
kJ
|
380000
Ws
|
390
kJ
|
390000
Ws
|
400
kJ
|
400000
Ws
|
410
kJ
|
410000
Ws
|
420
kJ
|
420000
Ws
|
430
kJ
|
430000
Ws
|
440
kJ
|
440000
Ws
|
450
kJ
|
450000
Ws
|
460
kJ
|
460000
Ws
|
470
kJ
|
470000
Ws
|
480
kJ
|
480000
Ws
|
490
kJ
|
490000
Ws
|
500
kJ
|
500000
Ws
|
510
kJ
|
510000
Ws
|
520
kJ
|
520000
Ws
|
530
kJ
|
530000
Ws
|
540
kJ
|
540000
Ws
|
550
kJ
|
550000
Ws
|
560
kJ
|
560000
Ws
|
570
kJ
|
570000
Ws
|
580
kJ
|
580000
Ws
|
590
kJ
|
590000
Ws
|
600
kJ
|
600000
Ws
|
610
kJ
|
610000
Ws
|
620
kJ
|
620000
Ws
|
630
kJ
|
630000
Ws
|
640
kJ
|
640000
Ws
|
650
kJ
|
650000
Ws
|
660
kJ
|
660000
Ws
|
670
kJ
|
670000
Ws
|
680
kJ
|
680000
Ws
|
690
kJ
|
690000
Ws
|
700
kJ
|
700000
Ws
|
710
kJ
|
710000
Ws
|
720
kJ
|
720000
Ws
|
730
kJ
|
730000
Ws
|
740
kJ
|
740000
Ws
|
750
kJ
|
750000
Ws
|
760
kJ
|
760000
Ws
|
770
kJ
|
770000
Ws
|
780
kJ
|
780000
Ws
|
790
kJ
|
790000
Ws
|
800
kJ
|
800000
Ws
|
810
kJ
|
810000
Ws
|
820
kJ
|
820000
Ws
|
830
kJ
|
830000
Ws
|
840
kJ
|
840000
Ws
|
850
kJ
|
850000
Ws
|
860
kJ
|
860000
Ws
|
870
kJ
|
870000
Ws
|
880
kJ
|
880000
Ws
|
890
kJ
|
890000
Ws
|
900
kJ
|
900000
Ws
|
910
kJ
|
910000
Ws
|
920
kJ
|
920000
Ws
|
930
kJ
|
930000
Ws
|
940
kJ
|
940000
Ws
|
950
kJ
|
950000
Ws
|
960
kJ
|
960000
Ws
|
970
kJ
|
970000
Ws
|
980
kJ
|
980000
Ws
|
990
kJ
|
990000
Ws
|
1000
kJ
|
1000000
Ws
|
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