Lecture 54 – Lecture 55 Electric Power Ozgur Unal NIS – PHYSICAL SCIENCE Lecture 54 – Lecture 55 Electric Power Ozgur Unal

Series and Parallel Circuits A circuit is a closed path that electric current flows. There are two kinds of circuits: Series Circuits and Parallel Circuits Series Circuits: In a series circuit, the current has only one loop to flow through. Series circuits are used in flashlights and some holiday lights (christmas trees).

Series and Parallel Circuits In a series circuits, if one of the components is broken, the current cannot flow  Open circuit Example: A burned-out light bullb causes an open circuit. Parallel Circuits: Parallel circuits contain two or more branches for current to move through.

Series and Parallel Circuits Consider the parallel circuit shown below. Which branch has higher current flowing through? Which branch has lower current Check out Figure 18!! What kind of circuit should be used to wire houses? http://www.educypedia.be/electronics/javabasic.htm

Household Circuits In a house many appliances draw current from the same circuit: More appliances  more current through the wires As the amount of current increases, so does the amount of heat produced in the wires  insulation may melt and bare wires can cause a fire! To protect against overheating of the wires, all household circuits contain either a fuse or a circuit breaker. A fuse contains a small piece of metal that melts if the current becomes too high  open circuit results A circuit breaker contains a piece of metal that bends when the current is too large  open circuit results

Electrical Power Electrical energy can be converted to other types of energies. Example: A fan converts electrical energy to mechanical energy A light bulb converts electrical energy to light and thermal energies. The rate at which electrical energy is converted to another form of energy is the electrical power. Electrical Power = Current x Voltage Difference (Watts) = (Amperes) x (Volts) P = I * V Example: A toaster oven is plugged into an outlet that provides a voltage difference of 120 V. What power does the oven use if the current is 10 A?

Electrical Energy = Electrical Power x Time Electrical energy consumed by an electrical device can be calculated using its power. Electrical Energy = Electrical Power x Time kWh = kW x hours E = P * t Example: A refrigerator operates on average for 10 h a day. If the power of the refrigerator is 700 W, how much electrical energy does the refrigerator use in one day? Example: Calculate the monthly cost of using this refrigerator if the cost per kWh is 0.09 $.