Chapter 7 discusses the relationship between electric current and potential difference, explaining potential difference as the work done per unit charge between two points in a circuit. It outlines Ohm's Law, which states that the current is directly proportional to potential difference in ohmic conductors, and highlights the roles of resistance and superconductivity in electrical systems. The document also explores the advantages of superconductors in technology, such as in maglev trains and MRI scanners.

1. CHAPTER 7: ELECTRICITY
7.1: Relationship
between electric current
and potential difference

2. What is potential difference?
is connected to a bulb
It creates an electric field along the wires

3. What is potential difference?
The positive terminal at P has a higher potential
The negative terminal at Q has a lower potential
Potential Difference, V
P Q

4. What is potential difference?
and lights the bulb
Potential Difference, V
P Q

5. What is potential difference?
Work is done
When electrical
energy carried
by the charges
is dissipated by
heat
and light energy
after crossing
the bulb

6. Potential Difference Equation
Potential Work Done
Difference, Charge
Or SI Unit:
Joule
Potential Energy
Difference, Charge

7. What is 1 Volt?
1 Volt = 1 Joule per Coulomb

8. What is 1 Volt?
1 Joule of work is done
1C
A B

9. Measuring Potential Difference
Must always
be connected
in parallel
Voltmeter
V

10. Measuring Current
Measures current
in Amperes
Ammeter
V
Must always
be connected
in series

11. Relationship between Current and
Potential Difference

12. Ohm’s Law
The electric current, I
flowing through a
conductor is directly
proportional to the
potential difference
across it if the
temperature and other
physical conditions are
constant

13. Ohm’s Law

14. Ohmic Conductors and Non-ohmic
Conductors
Conductors that obey Ohm’s Law: Ohmic
Conductors that don’t obey Non-
Ohm’s Law: Ohmic

16. Resistance
A measure of how much of a
conductor resists the flow of electricity

17. Resistance
Resistance (R) is defined as the ratio of
potential difference (V) across the
conductor the the current (I) flowing
through it.

18. Disadvantage of Resistance
Causes some
electrical energy to
turn into heat
So some electrical
energy is lost when
trying to transmit
across a conductor

19. Advantage of Resistance
Resistance allows us to use electricity
for heat and light
Heat generated from electric heaters
are due to resistance
Light we get from light bulb is due to
resistance of the wire
- filament becomes hot and glows

20. Ohm’s Law Equation
=
Resistance
V IR
Current
Potential
Difference

21. Super Conductor
Resistance of a metal
increases with temperature
Resistance of a semiconductor
decreases with temperature

22. Super Conductor
A material whose resistance becomes zero when its
temperature drops to a certain value called the critical
temperature

23. Advantages of a superconductor
Enables superconductors
to maintain a current
with no applied voltage
at that temperature

24. Advantages of a superconductor
Able to sustain large currents

25. Advantages of a superconductor
Enables superconductors
to maintain a current
with no applied voltage
at that temperature

26. Advantages of a superconductor
Able to sustain large currents

27. Advantages of a superconductor
Small sized motors and generators can be used

28. MAGLEV trains
Magnetic levitation
Trains can be made to
‘float’ on strong
superconducting
magnets
Eliminate friction between train and track

29. MRI Scanner
Magnetic
Resonance Imaging
Used to determine
what is going on
inside a human body
Body exposed to
strong superconductor
derived magnetic field
Hydrogen atoms release energy at a
frequency that can be read by a computer

30. Electrical power line
Electrical cable made of
superconductors increase efficiency
Reduce loss of energy from heat

31. Photo credits
• Flickr / kodak-moments--high-voltage / Matthias Pastwa
• Flickr / you can do it! / Eyfi
• Flickr / Idea / brunkfordbraun
• Flickr / Lightning May 2010 / Lightnomad
• Flickr / Old Altai Analogue Multimeter / Tudedude
• Flickr / RCA Porto-Arc Ammeter / Carbon Arc
• Flickr / resistance begins at OHM / ChrisM70
• BerndGehrmann at de.wikipedia [Public domain]/ Wikimedia Commons
• Flickr / Zeus Storm from ground level / dave~
• Flickr / Resistance Is Not Futile / maury.mccown
• Flickr / Resistance2 / steve_Iodefink
• Flickr / Failure / ‘PixelPlacebo’
• Flickr / img_1628 / LacerdaGonzo
• Flickr / experiments with liquid nitrogen / peletiah
• Flickr / Frozen – bicycle / #AlexWitt
• Flickr / Superconductor / rx8geek
• Flickr / afternoon tea for nerds / bionerd
• Flickr / superconducting maglev / wwu124
• Flickr / morning road / Todd Klassy
• Flickr / LHC magnets awaiting test / spadger
• Flickr / maglev / chill