Chapter 8.6 Electric Current
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What is an electric current?
Electric current is a flow of charged particles
What are conductor electrons?
Charge carriers: one or more electrons from each atom are free to move throughout the atomic lattice.
In fluids, what can constitute the flow of an electric charge?
Positive Ions and Electrons
Do protons more in a solid?
No they are bound within the nuclei of atoms and are in fixed positions
Where are electrons located in matter?
Every bit of matter, wires included, contains enormous numbers of electrons that swarm about in random directions.
When does an electric current occur?
When a source of voltage sets the electrons that are naturally in matter into motion, you get an electric current
What is an Ampere?
The rate of electrical flow is measured in amperes. It’s the rate of flow of 1 Coulomb of charge per second.
What is the drift speed of electrons in a typical circuit?
The speed of electrons as they drift through a wire is surprisingly slow. It’s much less than 1cm/sec
How fast does the electrical signal travel?
At the speed of light As soon as you close a switch in an electric circuit, the battery sends an electric field instantaneously through all parts of the circuit.
How fast is the electric field in the wire established?
At the speed of light
What is the net charge of a current carrying wire?
It has almost no net charge. Under ordinary conditions, the number of electrons and protons balance, so whether a wire carries a current or not, the net charge of the wire is normally zero at every moment.
How does electron circulation work with a battery?
The negative terminal of the battery repels the negative electrons and they move towards the positive terminal because of their attraction to positive charge
What is the direction of electrical current?
It’s from positive to negative- From the positive battery terminal, through the circuit, and toward the negative terminal
Where do flowing electrons get their energy from?
Chemical reactions in a battery. The electrons then deliver that energy to parts of the circuit, and then return to the battery with no energy before getting reenergized
What are electric conductors?
Substances (like metal) where electrons are loose enough to flow easily
Electric Insulators
Substances (like rubber or plastic) where the atoms hold their electrons tightly
Is current “used up” in an electrical circuit?
No The quantity that is used up in a circuit is not current, but energy
What is the difference between charge flowing through a circuit and voltage placed/impressed across a circuit?
Charge flows through a circuit because of an applied voltage across the circuit. Voltage doesn’t flow or go anywhere Charge is what moves Voltage produces a current, which makes the charge moves
What does voltage produce in a complete circuit?
Voltage produces a current (making charges move) through a complete circuit
What is Voltage?
Voltage is the pressure from an electrical circuit’s power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light. In brief, voltage = pressure, and it is measured in volts
Direct Current
Charges flowing in one direction Battery produces direct current in a circuit because the terminals of the battery always have the same sign
In a battery operated circuit, how do electrons move?
They move from the repelling negative terminal toward the attracting positive terminal, and they always move through the circuit in the same direction
What is an Alternating Current?
Electrons in the circuit are moved first in one direction and then in the opposite direction, alternating to and fro about relatively fixed position.
How does an alternating current occur?
It’s accomplished in a generator or alternator by periodically switching the sign at the terminals.