Unit 2 - Electricity Flashcards
What is the rule of Voltage in a Series Circuit
Vs = V1 + V2 + V3 …
What is the rule of Voltage in a Parallel Circuit
Vs = V1 = V2 = V3 …
What is the rule of Current in a Series Circuit ?
Is = I1 = I2 = I3 …
What is the rule of Current in a Parallel Circuit ?
Is = I1 + I2 + I3 …
What is the rule of Resistance in a Series Circuit
Rt = R1 + R2 + R3 …
What is the rule of Resistance in a Parallel Circuit ?
1/Rt = 1/R1 + 1/R2 + 1/R3 …
What are the 2 types of Current ?
Alternating Current
Direct Current
What is the definition of Current ?
Current is defined as the flow of charge passing by one point in 1s
What is the difference between Alternating and Direct Current ?
Alternating Current is constantly Changing Direction (positive and negative)
Direct current only travels in one direction (is only either positive or negative)
What is Ohm’s Law ?
Voltage = Current x Resistance
What is / are “Lost Volts” ?
Lost Volts are caused by a battery / power supply having a fixed value of internal resistance and when a Current is supplied this leads to a voltage, “Lost Volts”
What is “Electro-Motive-Force” ?
E.M.F is the supply voltage of the battery / power supply ?
What is meant by “an E.M.F of 10v” ?
I Volt is equal to 1 Joule per Coulomb
Therefore, 10Volts = 10 Volts is equal to 10 Joules of Energy firm to 1 coulomb of charge
What is the new (Vs = V1 + V2) equation in Higher ?
E.M.F = tpd + Lv
What happens when there is no current supplied to a circuit with internal resistance ?
There are no lost Volts
Therefore E.M.F = Tpd
What happens when a current is supplied to a circuit with internal resistance ?
There are Lost Volts
Therefore tpd tpd
What are the 2 types of Circuit ?
Series Circuit and Parallel Circuit
What is “Short Circuit Current” ?
Short Circuit Current is when the current is dangerously high as the current measured is only measured by the Internal Resistance.
Can be found by
- I = E.m.f / (internal Resistance)
- Graph, where it cuts the x-axis is
What is a capacitor ?
A Capacitor is:
An object which has the ability to store charge
What happens as a capacitor charges ?
As a capacitor charges it requires more energy to continue to fill the capacitor as like terms repel, therefore a potential difference is developed across the plates
What happens when a capacitor is fully charged ?
The potential difference across the plates is EQUAL to the supply voltage, therefore no Current is able to flow
What is the relationship for Capacitance and Voltage
C = Q/V
Capacitance = Charge(Q) / Voltage(V)
What is the measurement of a capacitor ?
Capacitance
What is the units of Change ?
Coulombs (C)
What is the Unit for Capacitance ?
Farads (F)
What happens to the current when there is a high Resistance ? And how does this affect the charging time of the capacitor ?
When there is high Resistance the Current is Low (I = V/R) therefore is the current is low the capacitor will take longer to charge
What happens to the current when there is a Low Resistance ? And how does this affect the charging time of the capacitor ?
When there is a Low Resistance the Current will be High, therefore the charging time of the capacitor will be short
What happens to the capacitor when it is Dis-charging ? And how does this affect the Voltage ?
When a capacitor is discharging it releases all of the charge sorted inside it, the voltage goes down from the Voltage supply back down to 0
What is the definition of Voltage ?
The energy given to each Coulomb of Charge (V = E/Q
Since Q is directly proportional to V the graph of Voltage against Charge forms a straight line through the origin ? What Equation can we derive from this ?
E = 1/2 x Q x V
What will the energy equation become if you have no value for Voltage ?
E = 1/2 x (Q^2 / C)
What will the energy equation become If you have no value for charge ?
E = 1/2 x C x V^2
What does adding a P-type impurity do to a semi-conductor ?
A regular Semi-Conductor consists of 4 Valence Electrons
A P-Type consists of 3 Valence Electrons therefore; when added to a pure semi-conductor it will create a hole in the Valence band, causing an electron to “fall” from the Conduction band into the valence band to fill this hole, leaving behind a hole in the conduction band to be filled by more electrons, creating more holes etc.
Thus reducing the resistance
Thus increasing Conductivity
What does adding an N-Type Impurity to a pure semi-conductor do?
A regular Semi-Conductor consists of 4 Valence Electrons
An N-Type consists of 5 Valence Electrons therefore when added to a pure semi-conductor, it will leave a free electron to roam around, which will find other atoms, it will become one of the 4 valence electrons of an atom which will cause and another electron to become free, to find another atom etc.
Thus reducing the resistance
Thus increasing Conductivity
What is layer called which is near the junction in which there are no free electrons or holes
The Depletion Layer
What happens in a Reverse Biased Junctiont
The effect is to “stretch” the depletion layer.
Therefore becoming less conductive - (I.e an insulator)
What happens in a Forward Biased Junction?
The Potential barrier will oppose the motion of electrons and Les. However, if the potential difference applied across the p-n Junction is great enough to overcome the potential barrier: electrons and holes will move through the depletion layer, allowing a current to flow the p-b junction
Therefore becoming more conductive than Reverse Bias
How do we know if a junction is Forward Bias or Reverse Bias ?
If Forward Bias the positive end of the P-N junction will match with the positive end of the cell / battery etc.
If Negative Bias the negative end of the P-N junction will match with the positive end of the call / battery etc.
What mode would the P-N junction be in if it is in Reverse Bias
PhotoConductive
If working in PhotoConductive mode, what does the P-N junction act as ?
The P-N Junction will act as an insulator
Light Dependent Resistor (LDR
What happens in an LDR ?
A photon of light comes in and “excites” electrons from the Valence band into the conduction band leaving a hole in the valence band for more electrons to fill causing the resistance to decrease therefore becoming more conductive
What happens when the P-N Junction is in “PhotoVoltaic” Mode ?
Acts as a Solar Cell, the light which operates from the P-N junction creates a Voltage
Creating an “Electron - hole pair”
What is an “Electron - Hole Pair” ?
The electrons (negative) go in one direction
the holes (positive) go in the other direction
Acting as a battery,
I.e electric charge goes 1 way, positive charge goes the other way
What is the “Band Theory” ? For both P-type and N-Type
When an N-Type impurity is added to a pure Semi-conductor, as N-type has 5 valence electrons it will cause an extra electron to move from the Valence band up to the conduction band which floats around and joins another atom with 4 valence electrons which causes another electron to become free, to find another atom to join, thus decreasing resistance, thus increasing the conductivity
When a P-Type impurity is added to a pure Semi-Conductor, as P-type has 3 valence electrons It will create a hole in the valence band and an electron will “fall” from the conduction band into the valence band, leaving behind the hole in the conduction band, and the hole in the conduction band will be filled by electrons, create more holes, to be filled with more electrons,
Thus decreasing resistance,
thus increasing conductivity
