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# 2.2 Analogue electronics. Resistors (5). Ohm's Law

OHM’S LAW connects resistance, voltage and current in an electrical circuit. There are many ways to express this relationship: with text, with formula and graphically.
Many materials contain some 'free' electrons which can move in response to an applied electric field. By attaching a pair of metal wires and applying a voltage between them we can move these charge carriers through the material. The result is a current whose magnitude depends on the characteristics of the piece of material and the applied voltage.Ohm's law says that the current we get is proportional to the potential difference between the wires. Most common conducting materials obey Ohm's law.

V= Voltage measured in Volts (V)

I= Current measured in Amperes (A)

R= Resistance measured in Ohms ()

a) The higher the resistance, the lower the current.
b) The higher the resistance, the higher the current.
c) The lower the resistance, the higher the current.
d) The lower the resistance, the lower the current.

Exercise 17: look at this graphical and construct a sentence Construct a sentence that makes sense for graph 10 Ohms and one for graph 20 Ohms. You must use the following: the lower, the higher, the resistance, the lower, the higher, the current,the voltage, for a given, voltage, current.

a) The ................................................................................................................................
b) The ................................................................................................................................

The Ω is too small for many resistors. Then we use the MULTIPLES kilo (k) and mega (M). Sometimes, to avoid reading errors, the letters R,k and M substitute the decimal point. Look at the examples.

 4k7 = 4.7 kΩ = 4,700 Ω5M6 = 5.6 MΩ = 5,600,000 Ω

Exercise 18

Give the value in Ω for the following resistors.
a) 6k8 =
b) 1M2 =