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Circuits - Coggle Diagram
Circuits
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Combining Resistors
Series
The total resistance of the circuit is equal to the sum of the resistors.
This is because the current passing through each resistor is the same, we know the p.d across each resistor is directly proportional to its resistance.
Parallel
When more resistors are connected it causes the total resistance of the circuit to decrease, as the current now has more paths to travel.
As the p.d across each resistor is constant, the resistors with higher resistance will have a smaller current passing through them.
Internal Resistance
When there is a current in a power source, work has to be done on the charges to move them through the power source. As a result some energy is lost and transferred to heat, and so the terminal p.d(the p.d measured at the terminals of the power source) is less than the e.m.f, the difference is called lost volts.
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Increasing the current through the power source means more charges travel through the cell and so more work is done by the charges, increasing the lost volts and lowering the terminal p.d.
A graph of terminal p.d against current has the gradient as negative internal resistance and the y-intercept as the e.m.f of the power source.
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