CHAPTER. Physics for Electricity. 3. Instructor Name: (Your Name ). Learning Objectives. Use Watt’s law to solve for electric power Discuss the concepts of electrical fields and magnetic lines of force Explain how an electron magnet is formed
Figure 3-1 Magnetic lines of force illustrated by iron filings.
Figure 3-2 Directional arrows on magnetic lines of force indicate direction the North end of a compass needle would point when placed in the magnetic field.
Figure 3-3 Unlike magnetic poles attract; like magnetic poles repel.
Figure 3-4 Lines of force around a current-carrying
Figure 3-5 Right hand rule of thumb
Figure 3-8 Magnetic field around conductor with 1 amp of current flow and 3 amps of current flow.
Figure 3-10 Magnetic field cancels out in the space between conductors with current flow in same direction. This causes two conductors to move toward each other.
Figure 3-11 Two conductors with 10A of current flowing through each conductor has the same combined magnetic field strength as 20A flowing through a single conductor.
Figure 3-12 Magnetic field around one loop of a conductor.
Figure 3-14 Adding an iron core to the coil to form an electromagnet.
Figure 3-16 Cutting magnetic lines of force to induce a voltage in the conductor: conductor is moving from the right to the left perpendicular to the magnetic lines of force.
Figure 3-17 Up and down movement of conductor parallel to magnetic lines of force resulting in no induced voltage because no magnetic lines of force are being cut by the conductor.
Figure 3-22 Magnetic field surrounding an inductor with no change in current flow.
Figure 3-23 Decreasing current flow through inductor
Lenz’s Law: The polarity of an induced voltage is such to oppose the change in current that produced it.
Figure 3-24 Current flow through an inductor is interrupted causing a reverse-polarity voltage to be induced across the inductor as the magnetic field surrounding the inductor collapses.
Figure 3-26 Inductor suppressed by parallel resistor limits the negative voltage spike to a low amplitude.
Figure 3-27 Transformer steps up a changing voltage: a transformer cannot increase a DC voltage.
Figure 3-28 Spark-ignition system utilizes a negative voltage spike and a type of transformer to produce thousand of volts.
Figure 3-33 Capacitor stores energy in the form of an electric field.
Figure 3-34 Capacitor charging.
Figure 3-35 Capacitor maintaining its charge.
Figure 3-36 Capacitor discharging.
Work = Force x Distance
Horsepower =(Torque x RPM) ÷ 5252
KE= ½ x Mass x Velocity²
GPE = Mass x Acceleration Due to Gravity x Height