Electric Currents Topic 5 1 Electric potential difference

Electric Currents Topic 5. 1 Electric potential difference, current and resistance

Simple Circuit • What does a simple circuit include? • Circuit implies a flow. What is flowing? • How do you know there’s a transfer of energy? • Can we see any of this?

Analogy

Advanced Analogy Energy Added to the System Energy Removed from the System

Definitions • What are charges? • How do we use charges to produce potential movement? • What happens when there is a charge in the middle?

Energy between metal plates • What needs to be done to move a negative charge from the red to blue plate? • What happens to the charge when it’s at the blue plate? • What happens when it’s released?

Potential Difference • Energy needed to move a charge from A to B

cell ☺ ☺ ☺ energy ☺ electron ☺ ☺ lamp ☺ ☺ ☺

Current • What is current? • How would we measure current? Conventional Current Electron Flow

Resistance • What is electrical resistance?

Ohm’s Law

Ohmic vs Non-Ohmic Resistors

Back to the Electric Circuit • Where does the energy come from in an electric circuit? • Where does the energy go? • What determines the amount of energy that is ‘taken’? • What is carrying the energy?

Definitions • Charge, Q • Current, I • Potential Difference, V (Voltage) • Resistance, R • If units of charge are coulombs [C], derive the units for I, V, and R

Definitions • 1 coulomb = 6 x 1018 electrons of charge • Current, I • Potential Difference, V (Voltage) • Resistance, R • If units of charge are coulombs [C], derive the units for I, V, and R

Definitions • 1 coulomb = 6 x 1018 electrons of charge • Current = Charge / Time • Potential Difference, V (Voltage) • Resistance, R • If units of charge are coulombs [C], derive the units for I, V, and R

Definitions • 1 coulomb = 6 x 1018 electrons of charge • Current = Charge / Time • Potential Difference = Energy / Charge • Resistance, R • If units of charge are coulombs [C], derive the units for I, V, and R

Definitions • 1 coulomb = 6 x 1018 electrons of charge • Current = Charge / Time • Potential Difference = Energy / Charge • Resistance = Voltage / Current or

Units •

The electron volt (e. V) • One electron volt (1 e. V) is defined as the energy acquired by an electron as a result of moving through a potential difference of one volt • 1 e. V = ? J

The electron volt (e. V) • One electron volt (1 e. V) is defined as the energy acquired by an electron as a result of moving through a potential difference of one volt • 1 e. V = 1. 6 x 10 -19 J

Inside the wire

Wire = Resistor • What happens when the electrons collide with the atoms? • What happens to the atoms when the wire is at a higher temperature? • How does this affect the resistance of the wire?

Power Dissipation • •

In summary