# Power, energy and efficiency

##### Intros
###### Lessons
1. Introduction to Power, Energy and Efficiency:
2. What is electric power?
3. What are the formulas relating to power?
4. What is electrical energy?
5. How can we measure the efficiency of an electric circuit?
6. What are the differences between voltage, power and energy?
##### Examples
###### Lessons
1. Solving for Power and Resistance

1. What is the power dissipated by resistor RA?
2. What is the resistance of RA?
2. Solving for Power, Current and Energy

1. What is the current leaving the battery?
2. How much energy is used by RB in 2 minutes?
3. Solving for Power and Voltage

1. What is the voltage of the battery supply?
2. What is the current going through RC?
3. What is the power dissipated by the circuit?
4. Solving for Power and Efficiency
An electric crane runs off of a 100V source at a current of 14A. The crane lifts a 180kg block 17.5m in the air (vertically) in 35 seconds. What is the efficiency of the crane?
1. Solving for Power and Efficiency
A lightbulb emits approximately 300 J of light energy in 5 seconds. If this bulb is 16% efficient, what is the power supplied to the lightbulb?