Chapter 28: DC Current and Circuits
Learning Goals
- Understand batteries and what they do.
- Know how to combine resistors in series and in parallel.
- Understand Kirchhoff's rules and how to apply them.
- Understand the time dependence of RC circuits.
Kirchhoff’s Laws
Multiloop circuits may be analyzed according to
Kirchhoff’s Laws
- Junction Rule: The sum of all currents entering any juction must equal
the sum of all currents leaving that junction
- Loop Rule: The algebraic sum of the potiential differences across
each element around any closed circuit loop is zero.
It is very important to note that a potential change may be positive or negative.
Resistor Combinations
Resistors connected in series have an
equivalent resistance given by
Resistors connected in parallel have an
equivalent resistance given by
RC Circuits
The current in a circuit consisting of a capacitor, resistor
and a constant applied voltage source all connected in series
has an exponential time dependence. In particular, when the
current is increasing,
When the current is decreasing,
