Current, Charge and Voltage

What is charge?
A property of certain particles. A particle with charge will experience a force in an electric field (or in a magnetic field if the charge is moving). Charge can be either positive or negative. Objects with a similar charge will repel.
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What is charge measured in?
Coulombs, C. The amount of charge on an object can be found using a coulomb meter.
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What is the charge of an electron?
It always has a negative charge of -1.6 x 10^-19 Coulombs.
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What is the charge on a Proton?
An equal but opposite charge to an electron.
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What is one coulomb of charge equal to in electrons?
6.25 x 10^18
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What is the Principle of the Conservation of Charge?
It is not possible to destroy or create charge. You can cancel out the effect of a charge on a body by adding an equal and opposite charge to it, but you can't destroy the charge itself.
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What is current electricity?
It is about moving charged particles. If you allow the charge that builds up in static electricity to flow you get current.
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What is current?
Current is the rate of flow of charge; it is the amount of charge flowing per second through a conductor.
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What is the equation for charge?
I=Q/t ; where I = Current (Amperes, A), Q = Charge flowing past a point in the circuit (Coulombs, C), t = Time taken for the charge to flow (Seconds, s)
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How can you get the Charge to flow?
First, you need to have a conductor for it to flow through and then you need to attract or repel the charged particles to make them move. The amount of attracting or repelling is measured in Volts and is called the voltage or Potential Difference
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What is voltage?
Work is being done on these charged particles to make them move, so the voltage is a measure of the amount of energy that is provided per coulomb of charge. 1 Volt - 1 joule per coulomb.
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What is the equation for voltage?
V=W/Q ; where V = Voltage (Volt, V), W = amount of energy (Joule, J), Q = Charge (Coulomb, C)
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What are the circuit rules?
As charge flows around a circuit they DON'T GET USED UP; it is the energy that the charged particles carry that decreases as they move around the circuit.
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What changes as the charge moves around the circuit?
Voltage
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What are the two types of circuits?
Series: The current is the same all the way around the circuit, The voltage is divided between the components in the circuit; Parallel: The current divides to travel along each loop, The voltage is the same across each loop.
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How do you measure the current in a circuit?
With an ammeter. It is placed in series in a circuit to measure the amount of charge flowing through it per second.
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How do you measure the voltage in a circuit?
With a voltmeter. It is placed in parallel to compare the potential at two different points, either side of the component. It can then measure the potential difference, or voltage across the component.
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What is current dependent on?
1) The speed at which charged particles are moving. 2) The charge they are carrying. 3) The number of charged particles that are moving.
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What is the drift velocity?
Charged particles do no move in a straight line through a conductor, because they collide with other particles in the material. We therefore use the average speed the particle travels at along the conductor.
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How do you calculate current with drift velocity?
I=vAnq ; where I = Current (A), v = Drift velocity (m/s), A = Cross-sectional area of the conductor (m^2), n - Charge density (m^3) This is the number of charge carriers that can move per m^3, q - Charge on each charge carrier (C)
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What makes a good conductor?
Good conductors such as metals have the most charge carriers. Semiconductors have about 1 x 10^10 times fewer charge carriers than metals. At low voltages insulators have no free electrons so that a current is unable to flow.
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Why are metals good conductors?
Electrons in the outer layers of the metal atoms are free to move from atom to atom. So if one end of a piece of metal is made positive, the electrons will be attracted towards it and because they are free, they can move towards it.
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Why does static charge only build up on insulators?
Materials that will not allow the flow of charged particles (nearly always electrons) through them. Insulators are materials made from atoms that HOLD ONTO THEIR ELECTRONS very strongly. The voltage across an insulator has to be high before can free.
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Why do semi-conductors not conduct as well?
They have far fewer electrons than metals. If they are given energy, electrons are able to free themselves from their atom and flow, which greatly reduces the resistance.
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Why are some semi-conductors light sensitive?
The light energy is able to free the electrons. There are about 5 naturally occurring semi-conductors.
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What are the equations for Charge and Work?
Q=It and W=QV
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What is: Q, I, t, W, and V?
Charge, C; Current, A; Time, s; Work, J; Potential Difference,V.
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Card 2

Front

What is charge measured in?

Back

Coulombs, C. The amount of charge on an object can be found using a coulomb meter.

Card 3

Front

What is the charge of an electron?

Back

Preview of the front of card 3

Card 4

Front

What is the charge on a Proton?

Back

Preview of the front of card 4

Card 5

Front

What is one coulomb of charge equal to in electrons?

Back

Preview of the front of card 5
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