This document discusses key concepts in circuits including potential difference, electromotive force, voltage, current, resistance, and Ohm's law. It states that Ohm's law defines the relationship between current, voltage, and resistance in a circuit. The document also describes series and parallel circuits, noting that in series circuits the current is the same in all parts while in parallel circuits the current divides between components.

1. Ohm’s Law
And the basics of CIRCUITS

2. The Concept of Potential Difference

POTENTIAL DIFFERENCE
- the work done or energy needed in moving a
unit electric charge between two points in an
electric field

Sources of Potential Difference
1. electric cells – uses chemical energy
2. generators – uses mechanical energy
3. solar cells (or photovoltaic cells) – uses light
energy

3. EMF vs.Voltage



Electromotive Force (emf)
- the potential difference between the terminals of a
cell when no current flows
Terminal Voltage (or simply voltage, V) or J/C
- the potential difference between the terminals of a
cell when current flows
Since a cell has an internal resistance that requires
energy (or potential difference) to overcome, then
the terminal voltage is always less than the
electromotive force.
( V < emf )

4. Current and Resistance

ELECTRIC CURRENT ( I )
- amount of charge passing through any point in a
conductor per unit time
I = Q / t unit: C/s or ampere (A); 1C/s = 1A

RESISTANCE ( R )
- the opposition a material offers to the flow of
charges
through it
- the SI unit of resistance is ohm (Ω) or J.s / C2
- named after George Simon Ohm

5. OHM’s LAW

it states that in an electric circuit; the
current (I) passing through a conductor
varies directly as the potential
difference (V) applied at its ends and
inversely as the resistance (R) of the
conductor; this maybe applied to the
entire circuit or to a particular part of a
circuit

6. OHM’s LAW
OPERATIONAL DEFINITION
I=V/R
Units: I --- amperes (A); 1A = 1C/s
V – volt (V)
R – ohm (Ω)

7. Simple Circuits



SERIES CIRCUIT
a simple circuit that contains
more than one piece of
electrical apparatus (or
resistors) connected one
after the other in a single
line
in this circuit, the current
flows in a single path and is
the same in all parts; and
the current stops flowing
whenever a part of the
circuit fails

8. Simple Circuits



PARALLEL CIRCUIT
a simple circuit where two or
more pieces of electrical
apparatus (or resistors) are
connected side by side so
that the current is divided
between them
in
this
circuit,
each
apparatus
operates
independently of the others
so even if one piece fails,
current still flows through the
others