Chapter+17,18+Circuits

Chapter 17,18 Electric Circuits by Emily Carey =**Vocab**=

**Chapter 17**
__average current__: the amount of charge divided by the time interval (SI unit is the __ampere__ or coulomb/second) __instantaneous current__: the limit of the average current as the time interval goes to zero (SI unit is the __ampere__) __drift speed__: the charge carriers move with a constant average speed __resistance__: the ratio of the voltage across the conductor to the current it carries (SI unit is ohms or 1V/A)


 * Ohm's Law**: many conductors for which the applied voltage is directly proportional to the current it causes

__resistor__: a conductor that provides a specified resistance in an electric circut __ohmic__: materials that obey Ohm's Law and have a constant resistance over a wide range of voltages __nonohmic__: materials that a resistance that changes with voltage or current __resistivity__: the constant of proportionality, noted in equations as //p// __temperature coefficient of resistivity__: how much the resistance changes with each degree of temperature change __power__: rate at which energy is supplied to a device __kilowatt-hour__: unit of energy used by electric companies in order to calculate consumption __superconductors__: metals and compounds that have resistances that fall to zero when below a certain temperature __electrocardiograph__: records voltage pulses created by muscular action in the heart __electrocardiogram (EKG)__: records patterns created by the electrocardiograph __implanted cardioverter defibrillatros (ICDs)__: electrical devices that can monitor, record, and process heart signals and then supply different corrective signals to hears beating at incorrect speeds

**Chapter 18**
__source of emf__: any device (battery or generator) that increases the electric potential energy of the charges in an electric circuit __open-circuit voltage__: the terminal voltage (voltage across the terminals of a power supply) when there is no current __load resistance__: the external resistance of a circuit

1) __The junction rule__: the sum of the currents entering any junction must equal the sum of the currents leaving that junction. (known as the conservation of charge) 2) __The loop rule__: the sum of the potential differences across all the elements around any closed circuit loop must be zero. (known as the conservation of energy)
 * Kirchhoff's Rules:**

__time constant__: the time required for the charge to increase from zero to 63.2% of its maximum equilibrium value in an RC circuit __neurons__: specialized cells in the body that form a complex network that receives, processes, and transmits information from one part of the body to another __dendrites__: input end of a neuron __axon__: a sort of tail on the neuron that transmits the signal away from the cell

=**Formulas**=

Chapter 18

 * Circuits with resistors in series**
 * Circuits with resistors in parallel**

[[image:parallel_formulas_for_resistors.jpg width="323" height="187"]]

 * Other formulas to keep in mind for Ch. 18**

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Multiple Choice
1) Find the value for I 1 a) 1.0 A b) 1.50 A c) .50 A d) 2.0 A

2) What is the value for I 2? a) 1.5 A b) 3.0 A c) 4.0 A d) 0.5 A

3) Find the value for I 3. a) 6.0 A b) 3.0 A c) 2.0 A d) 1.0 A

4) What direction is I 2 flowing? a) clockwise b) counterclockwise

5) What direction is I 3 flowing? a) clockwise b) counterclockwise