Parallel Circuit Sample Problem
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In the above problem R1 has a resistance of 100 ohms and R2 has a resistance of 10 ohms.  Knowing that solve the circuit for all parts assuming that 120 V is the power supply.  Use the Power Formula, Ohm's Law and rules of a parallel circuit to help!
The Rules of a  Parallel Circuit
1)  Voltage across parallel components is equal.

2)  Current splits between parallel elements depending on the ratio of the currency.

3)  Total resistance is always smaller than the smallest resistor.  There are two ways to find the total resistance in a parallel circuit.  If there are only two resistors, the product of the two resistors over the sum of the two resistors will give the correct resistance. .((R1 * R2)/(R1  + R2))  But in all situations the following equation works; 

Resistance/R Voltage/E Amperage/I Power/P
RT = 9.09 ohms ET = 120 V IT = 13.2 A PT = 1584 W
R1 = 100 ohms ER1 = 120 V IR1 = 1.2 A PR1 = 144 W
R2 = 10 ohms ER2 = 120 V IR2 = 12 A PR2 = 1440 W
Step By Step Guide
1. The first thing you want to do is calculate the product over the sum of the resistors in order to get the total resistance. 
(100*10)/(100+10) = 9.09 ohms

2. The next thing you want to find is the total current through the circuit.  Since you now have the total resistance and were given the total voltage which is 120V, all you need to do is plug everything into Ohm's Law.
120 V / 9.09 ohms = 13.2 A

3. To find the total wattage in the circuit you need to plug what you have into the Power Formula.  120 V * 13.2 A = 1584 W

4. The last thing you have to do is go through the circuit solving everything for each resistor.