Current of Electricity

• An electric charge is measured in coulomb (C) and is approximately 1.60x10^-19 C.
• The charge on a proton is +e

  The charge on an electron is -e
• Electric current consists of charges in motion from one region to another. Its SI unit is Ampere ( A ).
• In metals, current is due to the flow of electrons. However, by convention, the direction of current is in the direction of moving positive charges.
• Input the correct answer:

  A) electric current

  
• At room temperature, metals have electrons that are free to move randomly in all directions at high speeds within the constraints of the material.
• Electric current flowing through a conductor is the rate of flow of charges though it.
• $I =$$\frac{dQ}{dt}$ (in units)


  I = A

  Q = C

  t = s
• Q = It (in name)

  Q = Coulomb

  I = Ampere

  t = Seconds
• Input the correct symbols:

  A) A

  B) P

  C) v

  D) q

  
• I = nAvq (in name)

  I = Current

  n = Quantity of Charges

  A = Cross-sectional Area

  q = Charge
• A thin wire would have faster moving charge carriers than a thick wire, assuming that current is the same.
• When current I in a wire increases, only the drift velocity v increases.
• Assuming same length, greater cross-sectional area allows more room for charge carriers to flow through, hence increasing current.
• Thermal energy causes free charge carriers to move at high speeds; colliding against each other frequently and randomly. Under the influence of a potential difference, charge carriers gain an additional drift motion that carries them across the conductor. This is known as drift velocity.
• Electric current flows from a point of higher potential to a point in lower potential in an electric circuit.
• V = W / Q (in name)

  V = Potential Difference

  W = Energy

  Q = Charge
• The potential difference between two points in a circuit is the work done per unit charge when electrical energy is transferred to non-electrical energy when the charge passes from one point to another.
• The electromotive force of a source is the work done per unit charge when non-electrical energy is transferred into electrical energy when the charge moves around a complete circuit.
• Electromotive force is a source of energy and will exist regardless of a current flow in the circuit, whereas potential difference only exists when a current flows in the circuit.
• The resistance of a component is defined as the ratio of the potential difference across the component to the current passing through.
• R = V / I (in name)

  R = Ohm

  V = Volt

  I = Ampere
• Ohm's Law states that a current flowing through a conductor is directly proportional to the potential difference applied across the conductor, provided that physical conditions remain constant.
• When the current passing through a material increases, the temperature of the material is likely to increase.
• As temperature of the material increases, the number of charge carriers per unit volume increases, in turn decreasing the resistance of the material.
• As the temperature of the material increases, the thermal vibrations of the lattice atoms increases, in turn increasing the resistance of the material.
• Input the component's names that follow these I-V graphs:

  A) Metallic Conductor at Room Temperature

  B) Filament Lamp

  C) Semiconductor Diode

  D) Thermistor

  
• $R =$$\rho\frac{l}{A}$ (in name)


  R = Resistance

  $\rho$ = Resistivity

  l = Length

  A = Cross-sectional Area
• Resistivity has a SI unit of Ohm Metre ($\Omega m$).
• Power dissipated by a conductor is the product of the current passing through it and the potential difference across it.
• P = VI (in units)

  P = W

  V = V

  I = A
• $P =$$I^2R$ (in name)


  P = Power

  I = Current

  R = Resistance
• $P =$$\frac{V^2}{R}$ (in name)


  P = Power

  V = Potential Difference

  R = Resistance
• The rated power is the rate at which energy is used by a device when the device is operating at the rated potential difference across it.
• $E=$$I(r+R) \implies {V_R=R-Ir}$ (in name)?


  E = Power Supplied by Source

  I = Current

  r = Internal Resistance

  R = External Resistance

  $V_R$ = Potential Difference of External Resistor
• By the principle of conservation of energy,

  Power supplied by source = Power dissipated by internal and external resistors
• Maximum Power Theorem states that maximum power is supplied to the external circuit when resistance of the external circuit is equal to the internal resistance of the cell.
• Internal resistance is the resistance to movement of charge within an electrical power source causing energy loss in the source.