Voltage Is the Driving Force That Pushes the Current Around the Circuit
Potential Difference/ Voltage This is VOLTA. He studied the driving force that pushes current around a circuit. He gave his name to the unit of Potential Difference The unit of Potential Difference is the VOLT (V)
Voltage in a Series Circuit 12V The voltage in a series circuit is shared across each component. The sum of the voltages across each component equals the source voltage 4V
Electrical quantities in an electric circuit are related to each other by: OHM’S LAW OHM’S LAW says: If the source voltage remains constant, increasing the resistance in a circuit will cause a decrease in current flow in that circuit. In mathematical terms it tells us that current flow is inversely proportional to resistance. In equation form it says: Voltage (V) = Current (I) x Resistance (R) or V(in volts) = I (in amps) x R (in ohms)
Potential In volts (joules / coul) Current In amperes (coul / second) Resistance In ohms (volts / amp) Drop across a resistance Current passing through the resistor
V O L T A G E (volts ) Current (I) in amps II vv The slope of the Line gives the Resistance (Ω)
Factors Affecting Resistance 1.Thickness (diameter) of wire 2.Length of wire 3.Type of material 4.Temperature
Electron flow and Resistance Electricity in wires is a flow of electrons along the wire. As the electrons move along the wire they collide with the metal atoms. These collision make the atoms vibrate more…which makes the metal hotter. Resistance is a measure of how much a material tries to stop electricity passing through it.
CROSS SECTIONAL AREA -Thin wires have more resistance than thick wires -Halving (1/2) the cross sectional area of a wire doubles its resistance because there is half as much space for the electrons to move
Type of Material Different materials have different resistances. Example: A nichrome wire has more resistance than a copper wire of the same size (the atoms in nichrome hold the electrons more tightly than copper atoms)
Temperature As temperature increases, resistance increases.
Voltage –current for a lamp V/voltsI / amps 00 0.50.04 1.00.08 1.50.12 2.00.15 2.50.18 3.0 3.5 0.19 0.20 Plot these results What do they show?
Current-Voltage Graphs Show Resistance I V A Filament Bulb As the temperature of the filament increases, the resistance increases – hence the curve
Current-Voltage Graphs Show Resistance I V A Diode Current will only flow through in ONE DIRECTION (It has very high resistance in the reverse direction)
There is a Balance…. If you increase the Voltage – then more current will flow If you increases the Resistance – then less current will flow