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Electricity - Coggle Diagram
Electricity
Current and Charge
Electrical current is defined as the rate of flow of charge. It is the amount of charge passing a point in a circuit per unit time.
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Electrical charge is measured in coulombs, the coulomb is defined as the electric charge flowing past a point in one second when there is an electric current of one ampere.
Conventional Current - the current travels from a positive terminal to a negative one. The direction of all electric currents is still treated as from positive to negative, but the flow of electrons is in the opposite direction to conventional current.
An ammeter is used to measure the current in a circuit. It is place in series in the circuit and should has the lowest resistance possible so that it doesn't affect the current.
Kirchhoff's first law
The sum of the current going into a junction is equal to the sum of the current leaving the junction.
This is because of conservation of charge, and that is because of conservation of energy, that charge can not be created or destroyed.
Mean drift velocity
Number Density - the number of free electrons per cubic metre of material. the greater number of free electrons the better the electrical conductor.
Mean drift velocity is the average velocity of the charge carriers in a material. Not all of the charge carriers will move at the same velocity, as the electrons will collide with ions as they move through a material.
Mean drift velocity is affected by three factors, number density, current and the cross-sectional area of the material.
The narrower the wire, the faster the electrons move through it. this is because the current will stay the same , and so the mean drift velocity must increase.
Potential Difference
The potential difference is the amount of electrical energy being converted into other forms of energy, such as heat.
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A voltmeter is used to measure p.d. It is connected in series across a component. They have a large resistance to reduce the current that flows through it.
Electromotive Force
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The term electromotive force is used when charge carriers have gained energy from a power source. Non-electrical energy from the power source, such as chemical, is transferred to electrical energy to the charge carriers.
Resistance
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Resistivity
Resistivity is used to describe the electrical property of a material. Copper wires can have different resistances depending on their lengths and cross-sectional areas, but they all have the same resistivity.
The resistivity of a material varies with its temperature, as its temperature increases so does its resistivity.
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Types of Components
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Insulator - Have a very low number density or none at all, and so has a very high resistance.
Thermistor - a resistor that as its temperature increases, its resistance decreases. This is because as the temperature increases, more charge carries in the material are released, decreasing the resistance.
LDR - a resistor that as the light intensity shining on it increases, its resistance decreases. This is because as the light intensity increases, more charge carries in the material are released, decreasing the resistance.
