Another report of my classmate on our Electronics class.

1. Resistance
By Jillian Guadana

2. Resistance
– Resistance: opposes the push from the voltage
source. Resistance affects the speed of the current.
– Symbol for Resistance = R
– Unit for Resistance = Ohms (Ώ)

3. Georg Ohm (1789 – 1854)
– German physicist
– Ohm determined that there is a
direct proportionality between
the voltage applied across a
conductor and the electric
current.
– This relationship is known as
Ohm's law.

4. All materials resist current flow
to some degree. They fall into
one of two broad categories:
– Conductors: Materials that offer very little
resistance where electrons can move
easily. Examples: silver, copper, gold and
aluminum.
– Insulators: Materials that present high
resistance and restrict the flow of
electrons. Examples: Rubber, paper, glass,
wood and plastic.

5. "Resistance" may sound negative, but in
electricity it can be used beneficially.
Examples: Current must struggle to flow
through the small coils of a toaster, enough
to generate heat that browns bread. Old-
style incandescent light bulbs force current
to flow through filaments so thin that light
is generated.

6. Ohm’s Law
–State the relationship between current,
voltage, and resistance.
–German physicist George Ohm had the law
named after him, because of his extensive
research.

7. Resistance and
Current
–If the resistance in a circuit increases, the
current will decrease.
–If the resistance in a circuit decreases,
the current will increase.
–This is an inversely proportional
relationship.

8. – The lower the resistance, the higher the current
flow. Possible causes: insulators damaged by
moisture or overheating.
– The higher the resistance, the lower the current
flow. If abnormally high, one possible cause
(among many) could be damaged conductors due
to burning or corrosion. All conductors give off
some degree of heat, so overheating is an issue
often associated with resistance.

9. Examples…If you want to find Resistance in
Ohm’s:
R = V / I (ohms = volts divided by amps).
If V = 9 Volts and I = 4 A
Then R = 9 V/ 4A = 2.25 Ω

10. Example: