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# 19 ohm's law

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### Transcript of "19 ohm's law"

1. 1. Ohm’s Law And the basics of CIRCUITS
2. 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. 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. 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. 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. 6. OHM’s LAW OPERATIONAL DEFINITION I=V/R Units: I --- amperes (A); 1A = 1C/s V – volt (V) R – ohm (Ω)
7. 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. 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
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