Alexander-Sadiku
Fundamentals of Electric Circuits

	Chapter 1
	Basic Concepts

Basic Concepts - Chapter 1

	1.1 Systems of Units.
	1.2 Electric Charge.
	1.3 Current.
	1.4 Voltage.
	1.5 Power and Energy.
	1.6 Circuit Elements.

 1.1 System of Units (1)

 1.1 System of Units (2)

 1.2 Electric Charges

	Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C).
	The charge e on one electron is negative and equal in magnitude to 1.602 ´ 10-19 C which is called as electronic charge. The charges that occur in nature are integral multiples of the electronic charge.

 1.3 Current (1)

	Electric current i = dq/dt. The unit of ampere can be derived as 1 A = 1C/s.
	A direct current (dc) is a current that remains constant with time.
	An alternating current (ac) is a current that varies sinusoidally with time.  (reverse direction)

1.3 Current (2)

	The direction of current flow

1.3 Current (3)

	Example 1
	A conductor has a constant current of   5 A.
	How many electrons pass a fixed point on the conductor in one minute?

1.3 Current (4)

	Solution
	Total no. of charges pass in 1 min is given by
	5 A = (5 C/s)(60 s/min) = 300 C/min
	Total no. of electronics pass in 1 min is given

1.4 Voltage (1)

	Voltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts (V).
	Mathematically,                                     (volt)
		w is energy in joules (J) and q is charge in coulomb (C).
	Electric voltage, vab, is always across the circuit element or between two points in a circuit.
		vab > 0 means the potential of a is higher than potential of b.
		vab < 0 means the potential of a is lower than potential   of b.

1.5 Power and Energy (1)

	Power is the time rate of expending or absorbing energy, measured in watts (W).
	Mathematical expression:

1.5 Power and Energy (2)

	The law of conservation of energy

1.6 Circuit Elements (1)

1.6 Circuit Elements (2)

1.6 Circuit Elements (3)