Current and Resistance

This lecture is based on HRW, Sections 28.1 - 28.6. It covers more than we will discuss in class.

Electromotive force is just another way to say the voltage produced by a battery
Combining resistors in series produces an overall resistance of
```
             Req = R1 + R2 + .... + Rn
```

Combining resistors in parallel produces an overall resistance of

              1              1 
             --- = ------------------------
             Req   1/R1 + 1/R2 + ... + 1/Rn

Kirchoff's Rules permit one to solve for the current running through a complex circuit with batteries and resistors
1. The sum of currents entering a junction is equal to the sum of currents leaving that junction
2. The sum of voltages across circuit elements in any closed circuit loop is equal to zero
Applying Kirchoff's Rules to circuits often results in a set of simultaneous equations, which may be solved for the desired quantities

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