Defined the symbols and units for various physical quantities

46	C H A P T E R	O N E	t h e	c i r c u i t
			1.9
			▶	The discretization of matter into lumped elements such as batteries and

1. The boundaries of the discrete elements must be chosen so that

∂�B	0
∂t

∂q
∂t	=

where q is the total charge within the element.

3. The signal timescales must be much larger than the propagation delay of electromagnetic waves through the circuit.

▶ The associated variables convention defines current to flow in at the device terminal assigned to be positive in voltage.

1.9 Summary
The amount of energy w(t) consumed by a device over an interval of time

w(t) =	� t2	v(t)i(t)dt

where v(t) and i(t) are defined using the associated variables discipline. The unit of energy is the joule.

▶
▶

v = 0,

for the resistor with resistance R is

i = I.

▶ The representation of parameters in physical systems by their equivalent electrical circuit parameters has been discussed.