electrical curcuits
TRANSCRIPT
![Page 1: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/1.jpg)
ELECTRICAL CIRCUITS
All you need to be an inventor is a good imagination and a pile of junk.
-Thomas Edison
![Page 2: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/2.jpg)
Ohm’s Law
I = V / R
Georg Simon Ohm (1787-1854)
I = Current (Amperes) (amps)
V = Voltage (Volts)
R = Resistance (ohms)
![Page 3: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/3.jpg)
How you should be thinking about electric circuits:Voltage: a force that pushes the current through the circuit (in this picture it would be equivalent to gravity)
![Page 4: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/4.jpg)
Resistance: friction that impedes flow of current through the circuit (rocks in the river)
How you should be thinking about electric circuits:
![Page 5: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/5.jpg)
Current: the actual “substance” that is flowing through the wires of the circuit (electrons!)
How you should be thinking about electric circuits:
![Page 6: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/6.jpg)
Would This Work?
![Page 7: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/7.jpg)
Would This Work?
![Page 8: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/8.jpg)
Would This Work?
![Page 9: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/9.jpg)
The Central Concept: Closed Circuit
![Page 10: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/10.jpg)
circuit diagramcircuit diagram
cell switch
lamp
wires
Scientists usually draw electric circuits using symbols;
![Page 11: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/11.jpg)
Simple Circuits • Series circuit
– All in a row– 1 path for electricity– 1 light goes out and
the circuit is broken
• Parallel circuit– Many paths for electricity– 1 light goes out and the
others stay on
![Page 12: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/12.jpg)
1
2
3
![Page 13: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/13.jpg)
PARALLEL CIRCUIT
• Place two bulbs in parallel. What do you notice about the brightness of the bulbs?
• Add a third light bulb in the circuit. What do you notice about the brightness of the bulbs?
• Remove the middle bulb from the circuit. What happened?
![Page 14: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/14.jpg)
measuring current
Electric current is measured in amps (A)
using an ammeter connected in series in
the circuit.
A
![Page 15: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/15.jpg)
measuring current
A A
This is how we draw an ammeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT
![Page 16: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/16.jpg)
measuring voltage
The ‘electrical push’ which the cell gives to the
current is called the voltage. It is measured in
volts (V) on a voltmeter
V
![Page 17: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/17.jpg)
measuring voltage
V
This is how we draw a voltmeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT
V
![Page 18: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/18.jpg)
OHM’s LAW
• Measure the current and voltage across each circuit.• Use Ohm’s Law to compute resistance
Series Circuit
Voltage Current Resistance
Voltage Current Resistance
Parallel Circuit
![Page 19: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/19.jpg)
measuring currentSERIES CIRCUIT
PARALLEL CIRCUIT
• current is the same
at all points in the
circuit.
2A 2A
2A
• current is shared between the components
2A2A
1A
1A
![Page 20: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/20.jpg)
fill in the missing ammeter readings.
?
?
4A
4A
4A
3A?
?
1A
?
3A
1A
1A
![Page 21: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/21.jpg)
The circuit is no longer complete, therefore current can not flow
The voltage decreases because the current is decreased
and the resistance increases.
![Page 22: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/22.jpg)
The current remains the same. The total resistance drops in a parallel circuit as more bulbs are added
The current increases.
![Page 23: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/23.jpg)
Series and Parallel Circuits
• Series Circuits– only one end of each component is connected– e.g. Christmas tree lights
• Parallel Circuits– both ends of a component are connected– e.g. household lighting
![Page 24: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/24.jpg)
copy the following circuits and fill in the missing ammeter readings.
?
?
4A
4A
4A
3A?
?
1A
?
3A
1A
1A
![Page 25: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/25.jpg)
Different cells produce different voltages. The
bigger the voltage supplied by the cell, the bigger
the current.
measuring voltage
Unlike an ammeter, a voltmeter is connected
across the components
Scientist usually use the term Potential
Difference (pd) when they talk about voltage.
![Page 26: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/26.jpg)
V
measuring voltage
VV
V
![Page 27: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/27.jpg)
series circuit
1.5V
• voltage is shared between the components
1.5V
3V
![Page 28: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/28.jpg)
• voltage is the same in all parts of the circuit.
3V
parallel circuit
3V
3V
![Page 29: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/29.jpg)
measuring current & voltage
copy the following circuits on the next two slides.
complete the missing current and voltage readings.
remember the rules for current and voltage in series and parallel circuits.
![Page 30: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/30.jpg)
measuring current & voltage
V V
6V4A
A
A
a)a)
![Page 31: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/31.jpg)
measuring current & voltage
V
V
6V4A A
A
A
b)b)
![Page 32: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/32.jpg)
answers
3V 3V
6V
4A 4A6V
6V
6V4A 4A
2A
2A
4A
a)a) b)b)
![Page 33: Electrical curcuits](https://reader036.vdocument.in/reader036/viewer/2022062404/554a3432b4c90542548b585c/html5/thumbnails/33.jpg)
Voltage, Current, and Power
• One Volt is a Joule per Coulomb (J/C)
• One Amp of current is one Coulomb per second (6.24 x10^18 electrons/second).
• If I have one volt (J/C) and one amp (C/s), then multiplying gives Joules per second (J/s)– this is power: J/s = Watts
• So the formula for electrical power is just:
• More work is done per unit time the higher the voltage and/or the higher the current
P = VI: power = voltage current