lecture 9

lecture 9 - 20.9 Internal Resistance So far we've just...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
20.9 Internal Resistance So far we’ve just considered batteries and generators as contributing their emf to a circuit. In reality, they too have some resistance. This is called internal resistance, r . In batteries it’s due to the chemicals, and in generators it’s due to wire resistance. So, if a battery is connected to a load resistor, R , then the internal resistance, r , is in series with the load: Thus, the voltage across the ,g battery (known as the terminal voltage, V T ) is less than the full voltage V , since some is lost across r . otice: nd re in series! Thus, r T V V V = Notice: R and r are in series! V T Terminal voltage Battery voltage Voltage drop across the internal resistance, r
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Kirchhoff’s Rules In many circuits, applying the series or parallel methods is not sufficient to analyze them. There are two other rules we can use called Kirchhoff’s Rules : unction Rule urrent into a junction has to equal current out 1. Junction Rule Current into a junction has to equal current out. It is based on conservation of charge. I flows into junction, and I and I flow out, thus: 1 2 I 2 + I I 1 2 1 2. Loop Rule – Around any closed circuit loop, the sum of the potential (voltage) drops has to equal the sum of the potential rises. It is based on conservation of energy.
Background image of page 2
Here’s an example with the loop rule. We have a closed circuit loop with multiple batteries. What is the current in the circuit? 1. Choose the direction of the current(s) in each loop. Solution 2. Label the resistors from + to – in the direction of the current flow. Start at point A and go around the loop clockwise, and make a list of the potential drops and rises as we go all the way around.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 11

lecture 9 - 20.9 Internal Resistance So far we've just...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online