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It is a fact that more energy is burned when turning a light on, no matter what type, as the demand for current at that instant is higher, but for a short duration, meaning there is not a large consumption of energy.
On the other hand, in terms of the life of most fluorescent lights, turning them on has an effect as it wears away the cathode's emissive coat. The duration ratings for fluorescent lights are based on turning them on every three hours of use.
Fluorescent sources can now be considered for almost any area of the home and can be an economical choice over the long term. Although fluorescent tubes may come at a higher purchase price, they use 60 to 80 per cent less energy and last 10 to 20 times longer than incandescent bulbs. That translates into significant energy-cost savings and lower lamp replacement costs.
The following links contain more information concerning compact fluorescent light bulbs:
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Question: Can lightning also originate from the ground due to reverse polarity? Is there such a thing and if so, how does this happen? Nancy Taylor, Victoria, British Columbia
Lightning can indeed start from the ground. In fact, this is quite common. With any discharge of lightning there is a "return stroke". That is, if the lightning travels from the cloud to the ground, then it must return back from the ground to the cloud. This happens so quickly that most people only see the return stroke. If the lightning appears to originate from the ground then what you are seeing is the return stroke of the lightning travelling from the cloud to the ground.
Lightning is an electrical discharge caused when static electricity builds up between thunderclouds themselves, or between thunderclouds and the ground. Lightning strokes carry up to 100 million volts of electricity and leap from cloud to cloud, or cloud to ground and vice versa. Lightning tends to strike higher ground and prominent objects, especially good conductors of electricity such as metal. Lightning strikes the earth 50 -100 times every second.
In the northern hemisphere, most lightning occurs between June and August. The circumstances that lead up to a strike occur when hail and supercooled water droplets in a cloud collide, causing them to become electrically charged. The positively charged fragments are carried in the wind to the top of the cloud, while the negatively charged pellets collect in the bottom. Eventually, the two areas build up to such a point that a flash of electric current jumps across the gap.
This usually occurs within the cloud, but a third of the time it jumps from cloud to ground, creating an ionized channel. As it approaches the ground, this channel draws a charge of opposite polarity from a tall object on the ground-often a tree or tall building. When the two meet, the pathway is completed, and a spectacular flash of energy is funneled downward in the form of lightning. As the air in the pathway suddenly superheats to 30 000 C, it produces large sound waves of thunder.
Thunder is the noise caused by the explosive expansion of air due to the heat generated by a lightning discharge. Thunder may have a sharp cracking sound when lightning is close by, compared to a rumbling noise produced by more distant strokes. Because light travels at a faster speed than sound, you can see a lightning bolt before the sound of thunder reaches you.
For more information on lightning and thunderstorms please visit the following links:
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