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EE-2 Ohm’s Law
Ohm’s law deals with the relationship between current, voltage, and resistance.
The following expressions express this relationship, when I is current, R is resistance, and E is
voltage.
k Proportional Expression
The proportional expression is y = ax, where a is the constant of proportion. Doubling or tripling
x causes the y value to double or triple.
The following is the graph of the relationship between x and y.
The a variable in the proportional expression has a linear slope. The larger it value, the
greater the slope of the line is.
The graphs of y = 0.5x and y = 2x are shown below.
We can use these graphs to obtain the value of a. If the proportional expression graph
passes through a point where y = 9 and x = 3 (coordinates (3, 9)), for example, the value of a
is:
9 = a 3
a = 3 This means that the linear expression is y = 3x.
I = E / R R = E / I E = IR
y
y=ax
x
y
4
3
2
1
01234567
x
y=2x
y=0.5x
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