DC CIRCUITS - RESISTANCE/OHM'S LAW/NETWORK THEOREM

The property of the material that opposes the flow of an electric current.

Resistance

Formula of Resistance (Constant Temperature only)

Specific resistance or resistivity of Hard drawn copper (HDC) at 20^oc

1.77 × 10^-8 ohm-meter or 10.66 (ohm-cm)/ft

Specific resistance or resistivity of annealed copper at 20^oc

1.72 × 10^-8 ohm-meter or 10.50 (ohm-cm)/ft

Specific resistance or resistivity of aluminum at 20^oc

12.83 × 10^-8 ohm-meter or 17.0 (ohm-cm)/ft

area of circle?

Variation of resistance with the temperature

Temperature coefficient of resistance at 0^oc

Inferred absolute temperature of copper

T = -234.5 ^oc

Temperature coefficient of resistance at t1

1 inch = ______ mils

1000 mils

Temperature coefficient of resistance at t2

Change in temperature

T = t2 - t1

it states that the ratio of potential difference (V) between any two point on a conductor to the current (I) flowing through them is constant provided the physical conditions of the conductor does not change

ohms law

Enumerate the formula of series circuit characteristics

Enumerate the formula of parallel circuit characteristics

Current dividers

Voltage dividers

the amount of work required to maintain a current through a resistance for second is given by

Joule’s law of electric heating and

Formula of heat produce by electrical

Joule = ______ KJ/ kcal = ________ ft-lb/BTU

1Joule = ___ ergs = ____ gm-calories

it is the ratio of the heat actually utilized to the total heat produced electrically

Thermal efficiency

Formula of thermal efficiency

a group of cells that generate electric energy from their internal chemical reaction

battery

battery

1 ampere = _____ abampere

0.1 abampere

1ft² = _____cmil

183.35 ×10^6 cmil

Formula of Maximum Power Transfer

Pmax = V² /(4)(Rth)

1 liter = _____ m³

10^-3 m³

Cp of water = specific heat of water = _____j/kg°c

4200 j/kg°c

Density of water= ?

1000 kg

What is the other formula of R =pL²/V

R2/R1 = (L2/L1)²

What is the other formula of R =pV/A²

R2/R1 = (d1/d2)^4

What is the other formula of R =pL/A

R2/R1 = (d1/d2)²

Specific Resistance or resistivity of Silver

9.9 ohm-CM/ft

Specific Resistance or resistivity of Copper

10.37 ohm-CM/ft

Specific Resistance or resistivity of aluminum

17 ohm-CM/ft

Specific Resistance or resistivity of tungsten

33 ohm-CM/ft

Specific Resistance or resistivity of zinc

36 ohm-CM/ft

inferred absolute temperature of silver

243^oc

inferred absolute temperature of copper

234.5^oc

inferred absolute temperature of aluminum

236^oc

inferred absolute temperature of tungsten

202^oc

inferred absolute temperature of zinc

250^oc

temperature coefficient of silver at 20^oc

3.8×10^-3

temperature coefficient of copper at 20^oc

3.93×10^-3

temperature coefficient of aluminum at 20^oc

3.9×10^-3

temperature coefficient of tungsten at 20^oc

4.5×10^-3

temperature coefficient of zinc at 20^oc

3.7×10^-3

Insulation resistance of cables

Formula of conductance

Delta to wye transform

wye to delta tranform

6 Equal resistor : EQ resistance between any two terminal

Cubical -Connected 12 identical resistor - two terminals

Cubical -Connected 12 identical resistor - two terminals in diagonal

Cubical -Connected 12 identical resistor - two terminals in diagonally opposite

named after the German physicist, Gustav Robert Kirchhoff

Kirchhoff’s law

the algebraic sum of the currents at any junction or node of an electric circuit is zero

Current law (KCL)

the algebraic sum of the emf and the resistance voltage drop in any closed loop of an electric circuit is zero

Voltage law (KVL)

involves a set of independent loop currents assigned to “as many meshes” as it exist in the circuit

Maxwell mesh method

the current in any resist is equal to the algebraic sum of the current delivered by each independent sources assuming that each source is acting “acting alone or independently”

a circuit with “n” nodes, has a solution with only “n-1” number of equations needed.

Nodal node method