o

To find resistance:

This formula is a valuable one to remember because it makes understandable

many of the things that happen in an electrical circuit. For instance, if

the voltage remains constant, the current flow goes down if the resistance

goes up. An example of this would be a lighting circuit that is going bad

in a truck. Suppose the wiring circuit between the battery and the lights

has deteriorated, due to connections becoming poor, strands in the wire

breaking, switch contacts becoming dirty, or other similar problems. All of

these conditions reduce the electron path or, in other words, increases

resistance.

And, with this increased resistance, less current will flow.

The voltage of the battery stays the same (for example, 12 volts). If the

resistance of the circuit when new (including light bulbs) was 6 Ohms, then

2 amperes will flow. To satisfy the equation, 12 (volts) must equal amperes

times Ohms resistance (2 x 6). If the resistance goes up to 8 Ohms, only

1.5 amperes can flow. The increased resistance cuts down the current flow

and, consequently, the amount of light.

b. *Applying Ohm's Law. * By using Ohm's law, you are able to find the

resistance of a circuit, knowing only the voltage and the current in the

circuit.

In any equation, if all the variables (parameters) are known except one,

that unknown can be found. For example, using Ohm's law, if current (I) and

voltage (E) are known, resistance (R) (the only parameter not known) can be

determined as follows:

o

Formula:

Referring to figure 5 (on the following page), where E equals 10 volts and I

equals I ampere, solve for R, using the above equation:

o

Given:

E = 10 volts

I = 1 ampere

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