## Thursday, September 3, 2009

### Electrical Resistance

Electrical resistance is the ability of the material to resist the flow of current
Almost all materials have resistance. Even the best conductor such as gold have some resistance. Common materials that have resistance are light, motors in the fan and heater

Resistance, R of a conductor is defined as the ratio of potential difference, V across the conductors to the current, I flowing through it
Therefore,

Where, R = resistance measured in ohm (Ω)
V = voltage measured in volt (V)
I = current measured in ampere (A)

Example of calculation on using the formula

1. When a potential difference of 12 V is applied across a conductor, it is found that the current passing through the conductor is 0.2 A. What is the resistance of the conductor?
[Answer : 60 Ω]
2. Voltage across a 250 Ω resistor is 15 V. What is the current flowing through the resistor?
[Amswer: 0.06 A]
3. What is the potential difference across a light bulb of resistance 5 Ω when the current that passes through is 0.5 A?