Please enable JavaScript.
Coggle requires JavaScript to display documents.
ELECTRIC CURRENT AND DIRECT CURRENT CIRCUITS - Coggle Diagram
ELECTRIC CURRENT AND DIRECT CURRENT CIRCUITS
Ohm's Law and Resistivity
Resistivity is when a potential difference is applied across a conductor, the resistance of a conductor limits the current in the conductor.
Ohm's Law states that the steady current in a metallic conductor that is not a site of emf is directly proportional to the potential difference across the conductor if the temperature remains constant.
V/I = constant
A conductor that obey Ohm's Law is known as an ohmic conductor.
Variation of Resistance with temperature
The variation of resisteance with temperature for most metals is fairly linear and the resistance R at a temperature T may be represented by the equation R(T) = R0 ((1 + alpha(T-T0))
T0 is a selected reference temperature, R0 is the resistance at T0 and alpha is known as temperature coefficient of resistance of the material of the wire
Electromotive Force(emf), Internal Resistance and potential difference.
The emf of a source is the ratio of the total electrical power dissipated in the circuit in which the source is connected and the current in that circuit.
Sources of emf include the dry cell, battery, electric generator and solar cell.
The unit of emf is volt (v) or joule per coulumb (J/C)
The internal resistance (r) of a cell is the resistance to the flow of current because of the chemical reaction in the cell.
The internal resistance of a cell is a part of the total resistance in the circuit.The maximum current flow in the circuit depends on the internal resistance of the cell.
Electrical Energy and Power
Potential difference, V = energy dissipated/ charge
When a charge q flow through a potential difference of V, I=Q/t, Q=It
Energy dissipated= QV
=IVt (V=IR - I=V/R)
Energy dissipated = V^2/R times t
Electrical Power, P = electrical energy dissipated/time
P = I^2R = V^2 / R
V = P / I
Resistor in Series and in Parallel
Resistor in series, the same current I flow in all the resistors which is consistent with the principle of conservation of energy
When three resistor of resistance R1, R2, R3 are connected in parallel across PQ, the potential difference across the three resistors are the same E.
Kirchoff"s Law
JUNCTION - A point in a circuit where three or more conductors meet
LOOP - any closed conducting path.
Kirchoff's Junction Rule is based on the principle of conservation of charge.
ELECTRICAL CONDUCTION
Electric current flow from a higher electric potential to a lower electric potential
The current in the connecting wire is the rate of flow of charge through wire
The unit of current is ampere (A)