McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Electricity Principles & Applications Eighth Edition Richard J. Fowler Chapter 2 Electrical Quantities and Units (student version) McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. INTRODUCTION Charge »»» Coulomb Current »»» Ampere Voltage »»» Volt Resistance »»» Ohm Power »»» Watt (Page 17) (Page 9) 2 - 2

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Dear Student: This presentation is arranged in segments. Each segment is preceded by a Concept Preview slide and is followed by a Concept Review slide. When you reach a Concept Review slide, you can return to the beginning of that segment by clicking on the Repeat Segment button. This will allow you to view that segment again

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. ELECTRIC CHARGE (Page 17) 2 - 4

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview Charge (Q) is a quantity. (Page 18) Coulomb (C) is a base unit. (Page 18) Symbols are often used to represent quantities and units. (Page 18) 2 - 5

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. ELECTRIC CHARGE IS A PROPERTY POSSESSED BY BOTH ELECTRONS AND PROTONS Quantity is CHARGE (Q) (Page 18) Base Unit is COULOMB (C) (Page 18) Examples of correct usage: Charge = 15 Coulombs Q = 15 C 2 - 6

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review Charge (Q) is a quantity. Symbols are often used to represent quantities and units. Coulomb (C) is a base unit. Repeat Segment 2 - 7

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. CURRENT (Page 18) 2 - 8

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview What constitutes a current? What relationship exists between current, charge, and time? How does current flow in a solid? How does current flow in a liquid? 2 - 9

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Current is the movement of charge in a specified direction. (Page 18) Illustrations of current in a solid and a liquid follow:

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion - When an electron enters the + charge area, - an electron must leave the - charge area. - - Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. - Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion - - An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion __________________________ An electron moves from ion to ion. Ion

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved Ion An electron moves from ion to ion. Ion __________________________

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. _ + Current in a Liquid A salt electrolyte contains + sodium ions and - chlorine ions. Na + + Cl - - When the plates are connected to a source of - and + charges, the ions move toward the plate with an opposite charge. Cl - - Na + + Cl - - Na + + (Page 20)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Electric Current Terminology Quantity is CURRENT (I ) (Page 22) AMPERE (A) Base Unit is (Page 22) An ampere equals a coulomb per second. (Page 23) Examples of correct usage: Current = 12 Amperes I = 12 A

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Electric Current Relationships Charge Time Current = I = Q t (Page 23) Examples: Q I = t = 14 C 10 s = 1.4 A t = Q I = 14 C 1.4 A = 10 s

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Charge and Current Quiz The base unit of charge is the ____. The ____ is the base unit of current. The symbol for current is ____. The symbol for the coulomb is ____. Current in a solid causes ____ to move from ion to ion. When Q = 15 C and t = 5 s, the current equals ____. coulomb ampere I C electrons 3 A

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review What constitutes a current? What relationship exists between current, charge, and time? How does current flow in a solid? How does current flow in a liquid? Repeat Segment

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. VOLTAGE (Page 23)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview There are several definitions of voltage. A formal relationship exists between voltage, energy and charge. Symbols for quantities are italicized. Symbols for units are not italicized

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Voltage is the electric pressure or force that causes current. It is a potential energy difference between two points. It is also known as an electromotive force (emf). DEFINITION OF VOLTAGE (Page 23)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Voltage Terminology Quantity is VOLTAGE ( V ) Base Unit is VOLT ( V ) A volt equals a joule per coulomb. (Page 25) Examples of correct usage: Voltage = 32 Volts V = 32 V

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Voltage Relationships Voltage = V = Examples: Energy Charge W Q V = W Q = 56 J 2 C = 28 V Q = W V = 84 J 21 V = 4 C (Page 25)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Voltage Quiz Electromotive force is another name for ____. The base unit of voltage is the ____. The symbol for voltage is ____. The symbol for the volt is ____. A volt is equal to a ____ per ____. Q = ____ when W = 75 J and V = 15 V. W = ____ when V = 20 V and Q = 2.5 C. voltage volt V V joule, coulomb 5 C 50 J

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review There are several definitions of voltage. A formal relationship exists between voltage, energy and charge. Symbols for quantities are italicized. Symbols for units are not italicized. Repeat Segment

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. RESISTANCE (Page 27)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview Resistance is opposition to current. The base unit of resistance is the ohm. Four factors determine resistance. Resistivity is used when calculating the resistance of a given size of a material

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Definition Of Resistance Resistance is the opposition a material offers to current. (Page 27) Resistance is determined by: Type of material (resistivity) Temperature of material Cross-sectional area Length of material

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Some Factors That Determine Resistance For a specific material and temperature, this block has a given amount of resistance. Doubling the length of the block, Doubling the cross-sectional area, doubles the resistance. halves the resistance. (Page 28)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Resistance Terminology Quantity is RESISTANCE ( R ) OHM (  ) Base Unit is Examples of correct usage: Resistance = 47 ohms R = 47  An ohm equals a volt per ampere. (Page 28)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Resistance Relationships Resistance = R = Example: Resistivity x length area KL A R = KL A = = 0.1  1.4 x10 -6   cm x 2 x10 4 cm 0.28 cm 2 (Page 29)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review Resistance is opposition to current. The base unit of resistance is the ohm. Four factors determine resistance. Resistivity is used when calculating the resistance of a given size of a material. Repeat Segment

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. POWER (Page 30)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview Power is the rate of converting energy. The relationship between power, energy and time is P = W/t. The watt is the base unit of power. Symbols for power and watt are P and W

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Definition Of Power Power is the rate of using energy or doing work. (Page 31) “Using energy” means that energy is being converted to a different form. (Page 31)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Power Terminology (Page 31) Quantity is POWER ( P ) WATT ( W ) Base Unit is Examples of correct usage: Power = 120 Watts P = 120 W A watt equals a joule per second. (Page 31)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Power Relationships Power = P = Examples: Energy Time W t P = W t = 158 J 20 s = 7.9 W W = Pt = 75 W x 25 s = 1875 J (Page 31)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Resistance and Power Quiz A material’s opposition to current is called ____. The base unit of resistance is the ____. The base unit of power is the ____. The symbol for the ohm is ____. The rate of doing work is called ____. The symbol for the watt is ____. P = ____ when W = 160 J and t = 8 s. resistance ohm power watt W 20 W 

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review Power is the rate of converting energy. The relationship between power, energy and time is P = W/t. The watt is the base unit of power. Symbols for power and watt are P and W. Repeat Segment

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Multiple and Submultiple Units (Page 36)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview m = milli = k = kilo = M = mega = 10 6  = micro =

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Conversion Between Base, Sub, and Multiple Units To convert 300 mA to A,. move the decimal point three places to the left, and change mA to A. 300 mA To convert 5200 J to kJ,move the decimal point three places to the left, and change J to kJ J J J J kJ or 5. 2 kJ A or 0. 3 A To convert 0.04 V to mV, move the decimal point three places to the right V V V V and change V to mV mV or 40 mV (Page 36)

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Conversion Quiz mA equals ______ A. 4.7 k  equals ______ . 350 mV equals ______ V M  equals ______ k . 45  V equals ______ mV

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. Concept Review m = milli = k = kilo = M = mega = 10 6  = micro = Repeat Segment

McGraw-Hill © 2013 The McGraw-Hill Companies Inc. All rights reserved. REVIEW Charge »»» Coulomb Current »»» Ampere Voltage »»» Volt Resistance »»» Ohm Power »»» Watt