This document presents information about electrical circuits and their components. It discusses how batteries and generators convert different types of energy into electrical energy. It then describes common circuit components like light bulbs, motors, and speakers that convert electrical energy into other forms. The document goes on to explain key electrical concepts such as electric current, voltage, resistance, and Ohm's law. It provides examples of how circuits work and how measurements can be taken.

1. presents
a production
Everything Electric
Episode 2
Vaguely Voltage

2. Simple circuit
Source: chemical to electrical
Connection: conduct electricity
with almost no energy change
Component: electrical to
light and heat

3. Sources of electrical energy
They convert different types of energy to electrical energy
Batteries:
Chemical
to
Electrical
Image credit: Ian Britton @ FreeFoto.com
Image: US Department of Energy
Eel: Atomic power station:
Chemical Nuclear
to to
Electrical Electrical
Image: Aaron Gustafson @ flickr.com

4. Components
They convert electrical energy to different types of energy
produces heat energy
produces heat energy
produce light and
heat energy
produces sound, kinetic
and heat energy
produces kinetic
and heat energy

5. What is Electric Current?
Electric current is the flow of electric charge
Q
Ixt
Charge, Q is measured in coulombs (C)
Current, I is measured in amperes (A)
Time, t is measured in seconds (s)
One ampere = One coulomb per second
Current flowing = Charge passing ÷ time taken

6. Conventional current
electrons
electrons
electrons
electrons
Electrons travel around the circuit from - to + terminals of
the battery, but the arrows on the wires for the
conventional current are drawn the other way.

7. Symbols
They are easy to draw and everyone agrees what they look like

8. Parallel circuits 2
Think of them as Ladder circuits
Try this out: http://
phet.colorado.edu/en/
simulation/circuit-
construction-kit-ac
When a new component is
connected in parallel, the
current in the existing
components does not change,
although the current from the
battery will increase

9. Series circuits
Think of them as Chain circuits
This circuit contains 3 cells and 3 bulbs in series
What happens if you change the number of bulbs?
What happens if you change the number of cells?

10. Q: What happens if
you reduce the
number of bulbs
but keep the cells
the same?
A: The bulb gets brighter.
This means the electric
current is higher.

11. Q: What happens if
you reduce the
number of cells
but keep the bulbs
the same?
A: The bulbs get dimmer.
This means the electric
current is lower.

12. What is Voltage?
also known as potential difference
voltage is the energy transferred per unit charge passed
1 volt = 1 joule per coulomb
A battery of voltage 6.0 volts gives 6.0 joules
of energy to each coulomb which passes
Energy, E in joules
PD,V in volts E
Charge, Q in coulombs Q xV

13. Ammeters and voltmeters
To measure V and
I in the bulb...
A current flows through
the component
Ammeter connected in
series - you must break
the circuit to connect it
A voltage is applied
across the component
Voltmeter connected in
parallel - just touches
the wires at either side

14. Measuring V and I
Apply different voltages across a
component (this one is a bulb) by adding
more cells (or using a variable power
supply).
Circuits created at echalk.co.uk
Plot a graph of V
against I

15. Current in bulbs and resistors
Results for actual investigation using variable power supply

16. Current in diodes
Image: Erik Streb @ wikipedia
When the voltage is positive, the
diode conducts electricity, but
when the voltage is reversed, the
diode blocks the current.
Image: Theresa Knott @ wikibooks

17. Light emitting diodes
When the voltage is positive, the
diode conducts electricity, but
when the voltage is reversed, the
diode blocks the current
When current flows in
the LED, it emits light; if it
is connected in reverse,
no current will flow.
Image: Pete Scamper

18. What is Resistance?
Resistance is how much a conductor opposes the flow of current.
If the resistance is low, then the current is high.
If the resistance is high, then the current is low
Resistance, R is measured in ohms (Ω)
Voltage,V is measured in volts (V)
Current, I is measured in amps (A)
V
and... R=V/I
IxR

19. Ohm’s Law
The current through a metallic conductor is directly
proportional to the voltage across its ends if the
temperature and other conditions are constant.
Image: bbc gcse bitesize
Explore Ohm’s Law with PHET simulation

20. Light-Dependent Resistors
Also known as LDRs or photoresistors
When bright light shines on it, the
resistance is low and the current is high.
Image: ladyada.net
Image:
Benthewikiman
@ wikipedia

21. Thermistors
Also known as Negative Temperature Coefficient (NTC) Resistors
When the temperature is high, the
resistance is low and the current is high.
Image: Julong Technology Ltd
Image: Arroyo Instruments

22. How a circuit works
When the electrons return to Each coulomb takes 6.00 J of
the battery, all electrical energy electrical energy from the battery.
has been converted.
0.75 J Almost no
electric energy change
All 6.00 J has to light/ in the wire;
been converted heat still 6.00 J/C
from electric
energy.
3.00 J electric to light/ heat
Each coulomb loses
2.25 J electrical
energy to light and
heat in this bulb

23. a production
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+POTENTIAL+DIFFERENCE+IN+CIRCUITS