Warm-Up: April 13/14, 2016 A 9.0 V battery is connect to a 8250 Ω resistor. How much current flows through the resistor? What is the power consumed by the resistor? How much power is produced by the battery?

Homework Questions?

Series and Parallel Circuits Chapter 23 Series and Parallel Circuits

Series Circuit A series circuit has all current flowing through every device. Only one path for current to follow Does not include connected voltmeters The equivalent resistance for the entire circuit is the sum of all resistances

Series Circuit Diagrams

You-Try #1 Find the equivalent resistance. Find the current passing through each resistor. Find the electric potential difference across each resistor.

Parallel Circuits Parallel circuits have several paths for the current to follow There is different amounts of current flowing through different portions of the circuit The equivalent resistance is given by

Parallel Circuit Diagrams

You-Try #2 Find the equivalent resistance. Find the current passing through each resistor. Find the electric potential difference across each resistor.

Comparison of Series & Parallel A series circuit has all current flowing through every device. Parallel circuits have several paths for the current to follow

Series Circuits Parallel Circuits Constant current through every element Different ΔV across each element Adding more elements increases equivalent resistance Different currents through each path Constant ΔV across each path Adding more elements decreases equivalent resistance

Combined Series-Parallel Circuits Most real circuits have some elements in series and some in parallel

Kirchhoff’s Rules Kirchhoff’s first rule – the junction rule: The sum of all currents entering a junction must equal the sum of all currents leaving the junction. Kirchhoff’s second rule – the loop rule: The algebraic sum of changes in potential around any closed circuit path (loop) must be zero.

You-Try #3 Find the current through each resistor

Short Circuit A short circuit is when a circuit has very low resistance, causing very high current. More current  more heat If not prevented, this could cause a fire The term short circuit is commonly misused to describe any electrical problem

Warm-Up: Calculate the equivalent resistance of each of the following circuits.

Ammeters and Voltmeters Ammeters measure current Positioned in series with the measured current Voltmeters measure electric potential difference (voltage) Positioned in parallel to the measured V Multimeters are devices with the capability of measuring current, electrical potential difference, resistance, and sometimes other variables

Home Electricity – Fuse Boxes Too much current is bad! Old buildings have fuse boxes. A fuse is a short piece of metal that melts when too large of a current passes through it. Fuses must be replaced when overloaded.

Home Electricity – Circuit Breakers Newer buildings have circuit breakers. A circuit breaker is an automatic switch that opens when the current reaches a certain value. Circuit breakers can be switched back on, just like a light switch.

Home Electricity – GFI or GFCI Newer houses also have ground-fault circuit interrupters in kitchens and bathrooms. They can detect any difference in current flow and stop it to prevent some electrocutions. The individual outlet will have a “test” button and a “reset” button

Homework Read Chapter 23 Page 636 #36-47, 57-63, 77-81 Find out if your home has a fuse box or a circuit breaker, and if it has ground-fault interrupters. If possible, have a parent/guardian show you your fuse box or circuit breaker Optional advanced reading: OpenStax Chapter 21