Georg Simon Ohm : Georg Simon Ohm Georg Simon Ohm (1789 – 1854) was a German physicist. As a high school teacher, Ohm began his research with electrochemical cell, invented by Italian Count Alessandro Volta. Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential difference (voltage) applied across a conductor and the resultant electric current. This relationship is now known as Ohm’s law.
Measurable quantities That can Be obtained From electric Current : 1.Voltage
2.Electric Current
3.RESISTANCE Measurable quantities That can Be obtained From electric Current
ELECTRIC POTENTIAL: VOLTAGE (V) : ELECTRIC POTENTIAL: VOLTAGE (V)
CURRENT (I) : CURRENT (I)
RESISTANCE (R) : RESISTANCE (R)
Factors that affect the resistance of wires: : Factors that affect the resistance of wires:
Ohm’s Law : The potential difference, V, across the ends of
a given metallic wire in an electric circuit is directly
proportional to the current flowing through it, provided
its temperature remains the same.
This is called Ohm’s Law. In other words –
V ∝ I
or V = constant × I
or V = IR
S.I. Units of V, I and R
Voltage or potential difference (V) = Volt (V)
Current (I) = Ampere (A)
Resistance (R) = Ohm (Ω) Ohm’s Law
OHM’S LAW (2) : OHM’S LAW (2)
Voltage vs. Current for a Constant Resistance : Voltage vs. Current for a Constant Resistance The slope of the
Line gives the
resistance R = v /I
or rearranged
v = I x R
Plotting Ohm’s Law : Plotting Ohm’s Law
Plotting Ohm’s Law (2) : Plotting Ohm’s Law (2)
Ohm’s Law Memory Aid : Ohm’s Law Memory Aid To calculate one unit of electricity when the other two are known, simply use your finger and cover the unit you do not know. For example, if both voltage (V) and resistance (R) are known, cover the letter/(amperes). Notice that the letter V is above the letter R, so divide the resistor’s value into the voltage to determine the current in the circuit
Review of I, V and R : Current (I):Electric current is expressed by the amount of charge flowing through a particular area in unit time.
Potential Difference[voltage](V):. For flow of charges in a conducting metallic wire electrons move only if there is a difference of electric pressure – called the potential difference –along the conductor.
Resistance(R): It is a constant for the given metallic wire at a given temperature. Review of I, V and R
Slide 15: Thank You…..