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Slide 1

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W v pl Q P
V= R= R= I= I=
Q I A T v
v = Potential Different
Q = Charge
W = Word Done
R = Resistance
p = Resistivity
I = Current
l = Length
P = Power
A = Cross -Sectional Area
n = Number Density
q = charge on an electron 1.6 x 10-19…read more

Slide 2

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Resistivity is a properties of a material, it is a constant
Resistance is dependant on dimensions of a material e.g.
Length, Cross-Sectional area, Temperature
Ohms Law Resistivity
Voltage is directly 3 -2 -3
proportional to Current Kgm A S…read more

Slide 3

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The Relationship between pd and current
Although current and pd measure different things, they are related to each other. If we
connect a battery up to a length of resistance wire, we can measure the current through the
wire if we use 1, 2, 3, or 4 cells. The results of such an investigation are...
Number of PD across ends Current/A
Current (A)
Cells of wire/V 0.8
1 1.5 0.2 0.6
A 0.4
2 3.0 0.4
3 4.5 0.6
4 6.0 0.8 0 1.5 3.0 4.5 6.0 7.5
Pd (V)
The graph shows that there is a simple relationship between the pd
across the ends of the wire and the current through it ­ doubling the
pd doubles the current. Repeating the investigation with other wires
gives results that show a similar relationship between pd and current.
The graphs are always straight lines through the origin, although the
slopes are different.…read more

Slide 4

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Metal at Semiconductor
constant diode
Lamp ntc -
Filament Thermister…read more

Slide 5

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The Relationship between pd and current
The relationship between resistance, current and voltage was first discovered by the German
physicist Georg Ohm in 1826 and is called Ohm's law.
Provided the temperature and other physical factors remain constant, the current through
a wire is proportional to the potential difference across its ends
If we divide pd by the current through the wire, we get a constant resistance of the wire, and
represents its opposition to current of 1A flows through it when it has a of 1V across it.…read more

Slide 6

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Internal Resistance Voltage/v Current/i Resistance
Potato Experiment 0.0232 0.00226 0.0974
Cells and components has internal resistance 0.0249 0.00222 0.0892
0.0270 0.00220 0.0815
0.0290 0.00218 0.0752
0.0310 0.00216 0.0697
A 0.0330 0.00214 0.0648
0.0339 0.00213 0.0628
V…read more

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