Tag: electric power distribution

What are the relationships between Joules, Coulombs, Amperes, Volts, and Watts?

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What are the relationships between Joules, Coulombs, Amperes, Volts, and Watts?

A Joule is a unit of energy; the capacity to do work. A Coulomb is a quantity of electric charge; equal to about 6,250,000,000,000,000,000 elementary charges. An Ampere is a measure of current; equal to the passage of 1 Coulomb of charge each second. A Volt is a measure of the energy carried by each charge; equal to 1 Joule of energy per Coulomb of charge. A Watt is a measure of power; equal to 1 Joule per second. A current of 1 Ampere at a voltage of 1 Volt carries a power of 1 Watt. That is because each Coulomb of charge carries 1 Joule of energy (1 Volt) and there is 1 Coulomb of charge moving by each second (1 Ampere). That makes for 1 Joule of energy flowing each second (1 Watt).

Why does less current flow through a longer wire?

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Why does less current flow through a longer wire?

Wires obey Ohm’s law: the current flowing through them is proportional to the voltage drop across them. But the precise relationship depends on the wire’s length. A short wire will carry a large current even when the voltage drop across it is small because that wire has a small electrical resistance; it does not impede the flow of electricity very much. But a long wire has a large electrical resistance and will only carry a large current if the voltage drop across it is large. If you do not change the source of electrical power (e.g. a battery) and replace short wires with long wires, those wires will not be able to carry as much current.

What causes large electric resistances?

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What causes large electric resistances?

Thin wires or wires made of poor conductors. Some metals are simply better at carrying current without wasting energy than other metals. It has to do with how often a charge bounces off of a metal atom and loses energy. Copper, Silver, and Aluminum are good conductors while stainless steel and lead are pour conductors. Metals tend to become better conductors as you cool them and worse as you heat them. Semiconductors such as carbon (graphite) are poor conductors but have the reverse temperature effect. At low temperature they are poor conductors but become good conductors at high temperature.

Why is direct current so much better than alternating current?

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Why is direct current so much better than alternating current?

It depends on the situation. You cannot use a transformer with direct current, so in that sense, alternating current is better. But many electronic devices need direct current because they require a steady flow of charges that always head in the same direction. So there are times when you need DC and times when you need AC.

What does voltage rise mean?

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What does voltage rise mean?

When current flows through a battery or the secondary of a transformer, its receives power. Each charge leaves the battery with more energy than it had when it arrived. Since the energy of each charge has increased, the voltage (energy per charge) of the current has increased. Thus the current passing through the battery experiences a rise in voltage or a “voltage rise”.

What is resistance?

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What is resistance?

Resistance is the measure of how much an object impedes the flow of electricity. The higher an object’s resistance, the less current will flow through it when you expose it to a particular voltage drop. To use the water analogy, resistance resembles a constriction in a pipe. The narrower the pipe (higher the resistance), the harder it is to push water through that pipe. If you keep the water pressure constant (constant voltage drop) as you narrow the pipes (increase the resistance), then less water will flow (the current will drop).

What is the difference between current and voltage?

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What is the difference between current and voltage?

Current is the measure of how many charges are flowing through a wire each second. A 1-ampere current involves the movement of 1 Coulomb of charge (6,250,000,000,000,000,000 elementary charges) per second. Voltage is the measure of how much energy each charge has. A 1-volt charge carries 1 Joule of energy per Coulomb of charge. To use water in a pipe as an analogy, current measures the amount of water flowing through the pipe and voltage measures the pressure (or energy per liter) of that water.