Section 7.3 Electrical Energy Circuits are pathways for electricity to flow. – Unlike static electricity, which is short-lived and fast, current flowing in a circuit is or can be continuous. – Have 3 basic components A voltage source One or more devices that use electrical energy Conductive connectors like wires – Two different types Series Parallel

When a circuit is closed, electricity flows. When a circuit is open, no electricity can flow. Series circuit- – Only one loop or path for electrons to move through. If one item in the loop goes out, they all do. – Things like lamps with multiple bulbs are wired in series Or strings of decorative lights. – The same amount of current runs through the whole circuit.

Series circuit

Parallel circuits- – More than one path for the electrons to move through. If one item goes out, the others stay on. – Buildings are wired in parallel – Individual rooms are wired in parallel. – Voltage is the same in all branches but current is higher through branches with lower resistance.

Schematic diagrams:

Electricity in your house Wiring is done parallel circuits. Standard U.S. voltage is 120 v. – Some appliances require 240 v. Electric dryer Electric hot water heater. Electric stove.

Fuses and circuit breakers The more things that are plugged into a circuit, the more current that is drawn through the circuit. – This can produce too much heat and cause a fire. Fuses are one way to prevent an overheated circuit.

GFCI Ground fault circuit interrupter- like a circuit breaker but right at the point of use.

Fuses need to be replaced when they “blow”. What do you do if you don’t have any extras? Circuit breakers fixed that problem – A switch that flips off when too much current is drawn through the circuit. Contains a bi-metallic strip or an electromagnet.

Electric Power The rate at which an appliance converts electrical energy into other forms. – Thermal, kinetic, light, sound, etc. – Power is in watts which is equal to J/sec.

Electric Power Ex: The current in a dryer is 15 A when plugged into a 240 v outlet. How much power does the clothes dryer use?

Electrical Energy We have to pay for the electricity we use if we get it from an electric company. We are charged for the energy we use, not the power.

How electrical energy is measured Every building that uses electricity from an electric company has a meter, which is read every month, to determine how much energy is used.

Calculating electrical energy Ex: A coffee pot operates on 2 A of current on a 110 v circuit for 3 hours. Calculate the energy used. If this happens every day and it costs $.0522per kwh, how much will it cost to operate this coffee pot for a month?