| For practical purposes, it is often necessary to know the overall value
both of resistances connected in a series or parallel circuit, and the rate
of current flow.
Add another identical lamp into the circuit in series with the Lamp Lp1. The current flowing through the circuit will be halved and both lamps will glow at half brightness. See fig 7. |
 Fig 7 |
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Using Ohms law you can theoretically prove that you have doubled the resistance through the circuit and that the current flow will be halved. Total resistance Rt is given by adding the resistance of Lp1 to that of Lp2
The current flow will be given by
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practical illustration of Fig 7.Ohms law is an application of simple common sense. If you double a circuits resistance then you will halve the current flowing through the circuit. If you halve the resistance then you will double the current flow. |
To work out the voltage V2 across Lp1 use Ohms Law again or you could
use the knowledge that the sum of voltage drops in a series circuit added
together will equal the input voltage.
The sum of the voltages V1 and V2 equals the input voltage Vt.
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Having found the current flow it is easy to find the voltage drop V1 across
Lp2
By ohms law
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