BGS - 09. Electricity Flashcards
Electrical Charge
Electrons are NEGATIVELY CHARGED
REPEL other electrons
Remember
Electron = nEgative
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Electical Charge
Protons are POSITIVELY CHARGED
ATTRACT
Remember
Proton = Positive
Induction
Inducing a current in a wire by passing a magent through the wire wrapped up in a coil.
Stronger the magnet, the faster it moves, and the greater the number of coils, the GREATER the effect and the STRONGER the electrical current
Magnet causes negatively charged electrons to start flowing from one atom to the next.
Negatively charged electrons repel each other as they move along the coil
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Electrical Generators
If a magent stops moving through a coil of wires, the current will stop.
Generators are a means to keep a magnet moving and inducing a current
Example;
Bycle wheel generator or ‘dynamo’
Makes contact with wheel. As wheel turns, this turns the head touching the wheel
The head is attached to a magnet, which sits within a loop of soft iron core
A coil of wires is wrapped around the soft iron
As the magnet spins, it induces a current in the wire
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Resistance and Conductivity
Materials made up of closely packed, regular atoms and have loosely bound electrons are GOOD CONDUCTORS
Materials with firmaly attached electrons and/or widely spaced atoms with large gaps are GOOD INSULATORS
CONDUCTORS - easily induce electrical current
INSULATOR - do not easily induce electrical current
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Measuring Electricity
Rate of electricty flow = CURRENT
Current is measured in AMPERE or AMP (A)
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Measuring Electricity
The force inducing the current to flow is called the POTENTIAL DIFFERENCE
Potential Difference is measured in VOLTS (V)
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Measuring Electricity
The material the current passes through and obstruct the flow.
This is known as RESISTANCE
Resistance is measured in OHMS (Ω)
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Ohms Law
There is a set relationship between potential difference, resistance, and current.
Potential Difference (V) is a measure of how strong a force is ‘pushing’ electrons in a wire
The bigger the push, the faster the flow.
Resistance (R) is a measure of how hard a push is needed to get the flow going.
The greater the resistance, the less the flow.
An induced current (I) is the measure of the resulting flow
I V R
I = V / R
or;
R = V / I
or;
V = I x R
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Measuring Electricity
An ammeter is wired IN LINE
A voltmeter is wired IN PARALLEL
ammeter measures the amps flowing through a component
voltmeter measures the potential difference across the component
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AC & DC
DC = Direct Current
AC = Alternating Current
DC | Direct Current
Current travels in one direction
AC | Alternating Current
Currennt keeps reversing direction
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Electrical Power
The rate of electrical energy being transformed
i.e. A curent passing through a light buld meets the resistance of the light buld element. This causes it to heat up and emit photos of light energy.
The current is therefore being transformed into light energy
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Electrical Power
The rate of electrical energy being transformed is called ELECTRICAL POWER
Electrical Power is measured in WATTS (W)
Direct relationship between Power (P), Watts , and Current (I) Induced;
I = P / V
or;
V = P / I
or;
P = I x V
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Ohms Law and Electrical Power
We know that;
P = I x V
We also know that;
V = I x R
We can replace ‘V’ in the P = I x V equation with ‘I x R’ from the voltage equation, since they both are a measure of the same thing.
New equation becomes;
P = I x I x R or simplified
P = I² R
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Static Charge
If you were to remove or add a neutron from or to an atom, this would give it an imbalance
i.e. if you removed a neutron, there woudl be more protons making it POSITIVELY charged.
If you added a neutron, there would be more neutrons than protons, making it NEGATIVELY charged
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