Magnetic Fields and Forces

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1 Magnetic Fields and Forces

2 Electric fields are produced by static electric charges. Magnetic fields are produced by: A. Magnetic charges B. Electric Currents Only C. Magnets Only D. Both Magnets and Electric Currents

3 Electric fields are produced by static electric charges. Magnetic fields are produced by: A. Magnetic charges B. Electric Currents Only C. Magnets Only D. Both Magnets and Electric Currents

4 ConcepTest 20.1a Magnetic Force I A positive charge enters a uniform magnetic field as shown. What is the direction of the magnetic force? 1) out of the page 2) into the page 3) downwards 4) to the right 5) to the left x x x x x x v x x x x x x x x x x qx x

6 What is the direction of the magnetic force on a positive charge where v is the velocity of the charge and B is the direction of the magnetic field? A) Upwards B) Downwards C) Outwards (out of page) D) Inwards (into the page)

7 What is the direction of the magnetic force on a positive charge where v is the velocity of the charge and B is the direction of the magnetic field? A) Upwards B) Downwards C) Outwards (out of page) D) Inwards (into the page)

8 ConcepTest 20.2 Atomic Beams A beam of atoms (neutral) enters a magnetic field region. What path will the atoms follow?

9 ConcepTest 20.2 Atomic Beams A beam of atoms (neutral) enters a magnetic field region. What path will the atoms follow? Atoms are neutral objects whose net charge is zero. Thus they do not experience a magnetic force. Follow-up: What charge would follow path #3? What about path #1?

10 ConcepTest 20.4a Mass Spectrometer I Two particles of the same mass enter a magnetic field with the same speed and follow the paths shown. Which particle has the bigger charge? 3) both charges are equal 4) impossible to tell from the picture 1 2

11 ConcepTest 20.4a Mass Spectrometer I Two particles of the same mass enter a magnetic field with the same speed and follow the paths shown. Which particle has the bigger charge? 3) both charges are equal 4) impossible to tell from the picture 1 2 The relevant equation for us is: According to this equation, the R mv qb bigger the charge, the smaller the radius. Follow-up: What is the sign of the charges in the picture?

12 ConcepTest 20.6a Magnetic Force on a Wire I 1) left A horizontal wire carries a current 2) right and is in a vertical magnetic field. 3) zero What is the direction of the force 4) into the page on the wire? 5) out of the page I B

13 ConcepTest 20.6a Magnetic Force on a Wire I A horizontal wire carries a current and is in a vertical magnetic field. What is the direction of the force on the wire? 1) left 2) right 3) zero 4) into the page 5) out of the page Using the right-hand rule, we see that the magnetic force must point out of the page. Since F must be perpendicular to both I and B, you should realize that F cannot be in the plane of the page at all. I B

14 20.6 Force between Two Parallel Wires Parallel currents attract; antiparallel currents repel. If you can remember the Right Hand Grip Rule, then the force between parallel wires is like a handshake

15 ConcepTest 20.9b Field and Force II Two straight wires run parallel to each other, each carrying a current in the direction shown below. The two wires experience a force in which direction? 1) toward each other 2) away from each other 3) there is no force

ConcepTest 20.9b Field and Force II Two straight wires run parallel to each other, each carrying a current in the direction shown below. The two wires experience a force in which direction?

16 ConcepTest 20.9b Field and Force II Two straight wires run parallel to each other, each carrying a current in the direction shown below. The two wires experience a force in which direction? 1) toward each other 2) away from each other 3) there is no force The current in each wire produces a magnetic field that is felt by the current of the other wire. Using the right-hand rule, we find that each wire experiences a force toward the other wire (i.e., an attractive force) when the currents are parallel (as shown). Follow-up: What happens when one of the currents is turned off?

17 Electromagnetic waves

18 Light can be Dispersed into its individual wavelengths This is called the Spectrum

19 In a vacuum, the speed of sun rays is: A)is zero. B) is nearly m/s. C) depends on the frequency. D) depends on their amplitude.

20 In a vacuum, the speed of sun rays is: A)is zero. B) is nearly m/s. C) depends on the frequency. D) depends on their amplitude.

21 Which Electromagnetic waves travel the fastest? 1. X-rays 2. Red Light 3. Radio waves 4. Microwaves 5. All the same

22 Which Electromagnetic waves travel the fastest? 1. X-rays 2. Red Light 3. Radio waves 4. Microwaves 5. All the same

23 Electromagnetic waves and color To human eyes, light consisting of a mixture of all wavelengths will be what color? A. Red B. Yellow C. White D. purple E. Blue

24 Electromagnetic waves and color To human eyes, light consisting of a mixture of all wavelengths will be what color? A. Red B. Yellow C. White D. purple E. Blue

ConcepTest Clicker Questions. Chapter 27 Physics: for Scientists & Engineers with Modern Physics, 4th edition Giancoli

ConcepTest Clicker Questions. Chapter 27 Physics: for Scientists & Engineers with Modern Physics, 4th edition Giancoli ConcepTest Clicker Questions Chapter 27 Physics: for Scientists & Engineers with Modern Physics, 4th edition Giancoli 2008 Pearson Education, Inc. This work is protected by United States copyright laws