Kinda-sorta, but probably not.

Anything that has a stand-by mode, a built-in clock, A LED shining or anything like that will use a littlepower as long as it's plugged in.

It'll use a lot more power while actually being used, but it's possible that all that time on stand-by together will require as much energy as a few moments of usage.

A blender or a can opener are usually simple devices that don't have any clocks or indicator lights, so they are quite unlikely to use any power while in stand-by mode. A TV however will pull a few watts even if it isn't turned on.

Can manufacturers of early cans recommended using a cold chisel and hammer to open their cans, but users rarely had such tools available in the field when they wanted to eat.

The first "can openers" were often whatever device that the person already had, typically a knife or bayonet. These "can openers" were improvised in their use and were usually less than adequate.

On January 5, 1858, Waterbury native Ezra J. Warnerinvented the first tool specifically intended as a can opener (not some other tool being forced into this use). This was the first recorded patent (US patent No 19063) for a can opener. However, Warner's can opener was not a tool for household use, because it could be dangerous. Grocers opened the cans before they left the store.

The first can opener safe for household use was patented by William Lyman on July 12, 1870 (US patent No 105346).

In short, the answer is no.

The long answer (quoted from Wikipedia):

"Dedicated can openers appeared in the 1850s and were of a primitive claw-shaped or "lever-type" design. In 1855, Robert Yeates, a cutlery and surgical instrument maker of Trafalgar Place West, Hackney Road, Middlesex, UK, devised the first claw-ended can opener with a hand-operated tool that haggled its way around the top of metal cans"

Use the unglazed edge on the bottom of a pottery plate.

If you are asking for a substitute for a whet stone, and you don't have a lot of respect for the knife, you could try a grinder or a file. Placing the blade in nitric acid will leave the edge sharp and jagged. If you have a lot of time, you could get some jeweler's rouge and polish the blade to a fine edge.

-This was taken from Wikipedia-

During the first years of the French Revolutionary Wars, the notable French newspaper Le Monde, prompted by the government, offered a hefty cash award of 12,000 francs to any inventor who could come up with a cheap and effective method of preserving large amounts of food. The new, larger armies of the period required increased, regular supplies of quality food; limitations on food availability were among the factors restricting effective military campaigns to the summer and fall months. In 1809, the French confectioner Nicolas François Appert observed that food cooked inside a jar did not spoil unless the seals leak, thus developed a method of sealing food inside glass jars. The reason why food did not spoil was unknown at the time, since it would be another 50 years before Louis Pasteur demonstrated the role of microbes in food spoilage. However, glass containers presented challenges for transportation. Glass jars were largely replaced in commercial canneries with cylindrical tin or wrought-iron canisters (later shortened to "cans") following the work of Peter Durand (1810). Cans are both cheaper and quicker to make and much more resilient than fragile glass jars. Glass jars have, however, remained popular for some high-value products and in home canning.[1] Tin-openers were not to be invented for another thirty years - at first, soldiers had to cut the cans open with bayonets or smash them open with rocks. The French Army began experimenting with issuing tinned foods to its soldiers, but the slow process of tinning foods and the even slower development and transport stages prevented the army from shipping large amounts around the French Empire, and the war ended before the process could be perfected. Unfortunately for Appert, the factory which he had built with his prize money was burned down in 1814 by Allied soldiers invading France. Following the end of the Napoleonic Wars, the canning process was gradually put into practice in other European countries and in the United States. Based on Appert's methods of food preservation, Peter Durand patented a process in the United Kingdom in 1810, developing a process of packaging food in sealed airtight wrought-iron cans. Initially, the canning process was slow and labour-intensive, as each can had to be hand-made and took up to six hours to cook properly, making tinned food too expensive for ordinary people to buy. In 1824 meats and stews produced by the Appert method were carried by Sir William Edward Parry in his voyage to find a northwestern passage to India.

More information is available on Wikipedia under the keyword canning...