Blog 5: 10 points from pages 553-563

1.       The amount of current flow in a circuit, and therefore the amount of energy transferred to any useful device depends on two things:

  I) The potential different of the power supply (the amount of push).

  II) The nature of the pathway through the loads that are using the electric potential energy.

2.       Resistance = the measure of opposition to current flow.

3.       R = V / I
R = Resistance in volts/ampere
V = Potential Difference in volts (V)
I = Current in ampere (A)

4.       This is called Ohm’s law (R = V / I)

5.       The amount of current flowing through a resistor varies directly as the amount of potential difference applied across the resistor as long as other variables, such as temperature, are controlled.

6.       Thinner wire has a larger resistance than a thicker one

7.       Properties of conductors that affect the resistance:
I) length (The longer the conductor, the greater the resistance e.g. if length is doubled, resistance is doubled)
II) cross-sectional area (The larger the cross-sectional area or thickness of the conductor, the less resistant it has to charge flow e.g. if cross-sectional area is doubled, the resistance becomes half)
III) type of material (some material are better conductors e.g. if resistivity, the general measure of the resistance of a substance, is doubled, the resistance is also doubled)
IV) temperature (greater molecular motion during high temperatures increase the resistance)

8.       The gauge number of a wire indicates its cross-sectional area (small gauge number has a large cross-sectional area)

9.       Superconductivity = the ability of a material to conduct electricity without heat loss due to electrical resistance.

Kirchhoff’s Law

1.       Kirchhoff’s current law – The total amount of current into a junction point of a circuit equals the current that flows out of the same junction.

2.       Kirchhoff’s voltage law – The total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop.

3.       In any circuit, there is no net gain or loss of electric charge or energy.

4.       Resistance in Series à R_T = R₁ + R₂ + R₃ + … + R_N
N = the total number of series resistors in the circuit

5.       Resistance in Parallel à