 # © 2012 Pearson Education, Inc. { Chapter 26 DC Circuits.

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© 2012 Pearson Education, Inc. { Chapter 26 DC Circuits

© 2012 Pearson Education, Inc. Charging a capacitor The time constant is  = RC. The time constant is  = RC.

© 2012 Pearson Education, Inc. Discharging a capacitor

© 2012 Pearson Education, Inc. You wish to study a resistor in a circuit. To simultaneously measure the current in the resistor and the voltage across the resistor, you would place Q26.8 A. an ammeter in series and an voltmeter in series. B. an ammeter in series and an voltmeter in parallel. C. an ammeter in parallel and an voltmeter in series. D. an ammeter in parallel and an voltmeter in parallel.

© 2012 Pearson Education, Inc. You wish to study a resistor in a circuit. To simultaneously measure the current in the resistor and the voltage across the resistor, you would place A26.8 A. an ammeter in series and an voltmeter in series. B. an ammeter in series and an voltmeter in parallel. C. an ammeter in parallel and an voltmeter in series. D. an ammeter in parallel and an voltmeter in parallel.

© 2012 Pearson Education, Inc. A battery, a capacitor, and a resistor are connected in series. Which of the following affect(s) the maximum charge stored on the capacitor? Q26.9 A. the emf  of the battery B. the capacitance C of the capacitor C. the resistance R of the resistor D. both  and C E. all three of , C, and R

© 2012 Pearson Education, Inc. A battery, a capacitor, and a resistor are connected in series. Which of the following affect(s) the maximum charge stored on the capacitor? A26.9 A. the emf  of the battery B. the capacitance C of the capacitor C. the resistance R of the resistor D. both  and C E. all three of , C, and R

© 2012 Pearson Education, Inc. { Chapter 27 Magnetic Fields and Forces

© 2012 Pearson Education, Inc. Magnetic poles  Figure 27.1 at the right shows the forces between magnetic poles.

© 2012 Pearson Education, Inc. Magnetism and certain metals  Either pole of a permanent magnet will attract a metal like iron, as shown in Figure 27.2 at the right.

© 2012 Pearson Education, Inc. Magnetic field of the earth  The earth itself is a magnet. Figure 27.3 shows its magnetic field.

© 2012 Pearson Education, Inc. Magnetic monopoles Breaking a bar magnet does not separate its poles, as shown in Figure 27.4 at the right. Breaking a bar magnet does not separate its poles, as shown in Figure 27.4 at the right. There is no experimental evidence for magnetic monopoles. There is no experimental evidence for magnetic monopoles.

© 2012 Pearson Education, Inc. Electric current and magnets In 1820, Hans Oersted discovered that a current-carrying wire causes a compass to deflect. (See Figure 27.5 at the right.) In 1820, Hans Oersted discovered that a current-carrying wire causes a compass to deflect. (See Figure 27.5 at the right.) This discovery revealed a connection between moving charge and magnetism. This discovery revealed a connection between moving charge and magnetism.

© 2012 Pearson Education, Inc. Magnetic force as a vector product We can write the magnetic force as a vector product (see Figure 27.7 below). We can write the magnetic force as a vector product (see Figure 27.7 below). The right-hand rule gives the direction of the force on a positive charge. The right-hand rule gives the direction of the force on a positive charge.

© 2012 Pearson Education, Inc. A beam of electrons (which have negative charge q) is coming straight toward you. You put the north pole of a magnet directly above the beam. The magnetic field from the magnet points straight down. Which way will the electron beam deflect? A. upward B. downward C. to the left D. to the right E. It won’t deflect at all. A27.1 N Beam of electrons coming toward you

© 2012 Pearson Education, Inc. Q27.2 When a charged particle moves through a magnetic field, the direction of the magnetic force on the particle at a certain point is A. in the direction of the magnetic field at that point. B. opposite to the direction of the magnetic field at that point. C. perpendicular to the magnetic field at that point. D. none of the above E. One of A or B above, depending on the sign of the particle’s electric charge.

© 2012 Pearson Education, Inc. A27.2 When a charged particle moves through a magnetic field, the direction of the magnetic force on the particle at a certain point is A. in the direction of the magnetic field at that point. B. opposite to the direction of the magnetic field at that point. C. perpendicular to the magnetic field at that point. D. none of the above E. One of A or B above, depending on the sign of the particle’s electric charge.

© 2012 Pearson Education, Inc. A particle with a positive charge moves in the xz-plane as shown. The magnetic field is in the positive z-direction. The magnetic force on the particle is in Q27.3 A. the positive x-direction. B. the negative x-direction. C. the positive y-direction. D. the negative y-direction. E. none of these

© 2012 Pearson Education, Inc. A particle with a positive charge moves in the xz-plane as shown. The magnetic field is in the positive z-direction. The magnetic force on the particle is in A27.3 A. the positive x-direction. B. the negative x-direction. C. the positive y-direction. D. the negative y-direction. E. none of these

© 2012 Pearson Education, Inc. Magnetic flux calculations Example – calculate field strength of constant magnetic field through surface with area 3.0 cm 2 if total magnetic flux is 0.90 mWb