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General Values and Vectors by S.S. Education, Kota |
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ELECTRIC CHARGES AND FIELDS S.S. Education, Kota |
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CAPACITANCE by S.S. Education, Kota |
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RESISTANCE by S.S. Education, Kota |
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CURRENT by S.S. Education, Kota |
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MAGNETISM by S.S. Education, Kota |
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INDUCTIVE & RCL CIRCUITS by S.S. Education, Kota |
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AC CIRCUITS by S.S. Education, kota |
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ELECTROMAGNETICS by S.S. Education, Kota |
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CURRENT
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Current Density: [A/m2]
i = ∫ J × dA
if current is uniform
and parallel to dA,
then: i = JA
J =(ne) Vdd
i = current [A]
J = current density [A/m2]
A = area [m2]
L = length of conductor [m]
e = charge per carrier
ne = carrier charge density [C/m3]
Vd = drift speed [m/s]
Rate of Change of Chemical Energy in a Battery:
P = ie P = power [W]
i = current [A]
e = emf potential [V]
Kirchhoff’s Rules
1. The sum of the currents entering a junctions is equal to
the sum of the currents leaving the junction.
2. The sum of the potential differences across all the
elements around a closed loop must be zero.
Evaluating Circuits Using Kirchhoff’s Rules
1. Assign current variables and direction of flow to all branches of the circuit. If your choice of direction is incorrect, the result will be a negative number. Derive equation(s) for these currents based on the rule that currents entering a junction equal currents exiting the junction.
2. Apply Kirchhoff’s loop rule in creating equations for different current paths in the circuit. For a current path beginning and ending at the same point, the sum of voltage drops/gains is zero. When evaluating a loop in the direction of current flow, resistances will cause drops (negatives); voltage sources will cause rises (positives) provided they are crossed negative to positive—otherwise they will be drops as well.
3. The number of equations should equal the number of variables. Solve the equations simultaneously.
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